Amazon Arbitrage Minimum Prices: Set Your Floor Correctly

Sooner or later, most arbitrage sellers who reprice without a correctly calculated minimum price sell a unit below cost. The repricer did exactly what it was configured to do. The configuration was wrong.

The minimum price is the only barrier between a competitive pricing event and a margin-negative sale. If a competitor drops below your break-even, a repricer without a correct floor follows them. One with a correct floor holds.

TL;DR

The floor for Amazon arbitrage is (sourcing cost + prep cost + inbound shipping + FBA fee) divided by (1 minus referral fee rate minus target margin rate). Each lot has its own sourcing cost, so each lot can have its own floor. Where two lots are active at once, set the minimum to the higher floor, or to the MAP price if one applies and is higher. Match the rule type to the number of FBA sellers on each listing, test in Safe Mode for 7 days, then check price, Featured Offer Percentage and average selling price at hours 12, 24 and 48 after going live.

Floor = ($6.99 + $0.50 + $0.40 + $3.18) divided by (1 minus 0.15 minus 0.20) = $11.07 divided by 0.65 = $17.04 (rounded up).

Check at $17.04: the referral fee is $2.56, so total costs are $13.63 and net profit is $3.41, or 20.0% of the price. Any price below $17.04 earns less than 20%, or loses money.

Common floor calculation errors in arbitrage

Forgetting prep costs understates the floor. Leave out the $0.50 and the floor drops to $16.27. Sell at that price while still paying for prep and the net margin is 17.0%, not 20%, a shortfall of $0.65 a unit. Across 200 units that is $130 of missing profit from one overlooked cost.

How to handle per-lot sourcing cost variation

The scenario

• Lot 1: 20 units at $6.99. Floor = $17.04 (from the worked example).

• Lot 2: 30 units at 8.49.Floor=(8.49 + $0.50 + $0.40 + $3.18) divided by 0.65 = $12.57 divided by 0.65 = $19.34.

Both lots are active in FBA, and the ASIN has one minimum.

Option 1: set the floor to the higher lot ($19.34). This protects all inventory, and Lot 1 earns 27.8% instead of 20%. The trade-off is losing the Buy Box to anyone pricing between $17.04 and $19.33.

Option 2: set the floor to the lower lot ($17.04). This competes harder on Lot 1 but exposes Lot 2, where a unit at $17.04 earns $1.91, an 11.2% margin.

Option 3: pass per-lot costs from a sourcing tool. See the OAGenius and ArbitrageBoss section below.

Option 4: use a weighted average cost. ((20 x $6.99) + (30 x $8.49)) divided by 50 = 7.89.Theflooris(7.89 + $0.50 + $0.40 + $3.18) divided by 0.65 = $18.42. It is simple to maintain, but Lot 2 units can still sell up to $0.92 below their own floor.

The conservative recommendation: until per-lot floors are automated, use the highest active lot's floor. The margin given up on the cheaper lot costs less than the margin lost on below-floor sales.

The OA repricing playbook

Why OA competition differs and why undercut rules punish OA sellers

OA sellers often pick products because few sellers are on the listing. With two or three FBA sellers, each holds a large share of the Buy Box, so one price move is a big signal to the others.

An undercut rule moves your price below the lowest competitor by a set step. On a crowded listing that can make sense, because you must sit inside the competitive range to win any Buy Box time. On a two-seller listing it starts a spiral: you undercut by $0.10, the other tool undercuts by $0.10, and within hours both sellers are on their floors. Matching gives the other tool no reason to react, as the repricing rules guide explains. Check the rule on each OA ASIN rather than assuming one rule suits the catalogue.

The correct rule type by competitive density

Count the active FBA sellers on each ASIN before you choose the rule type. These bands are starting points to test in Safe Mode, not Amazon or Repricer.com figures.

In every band the per-ASIN floor is the lower bound, and an undercut rule is the wrong default. The features page lists eight rule types, including a Buy Box winner rule that raises your price in steps while you own the Box, which is the closest match to a ceiling hunt.

Velocity vs margin when inventory is limited

With a small lot every sale matters twice: once for the margin, and once for the pace at which it clears stock before storage fees build.

Amazon charges an aged inventory surcharge on stock held for 181 days or more. According to Amazon's seller forum, it starts at $0.50 per cubic foot for 181 to 210 days and rises to $5.45 per cubic foot for 271 to 300 days. For a 0.5 cubic foot unit that is $0.25 a month at the first rate and about $2.73 at the second, against the $3.41 unit margin in the worked example. Check current rates in Seller Central.

Turn the deadline into a pace. A 15-unit lot that must clear by day 180 needs a sale about every 12 days. One that must clear by day 90 needs a sale about every 6 days. Compare actual sales with that pace.

• Ahead of the pace: hold margin. Do not give away $2 a unit for sales that will happen anyway.

• On the pace: keep the target margin floor, with a ceiling hunt where competition is thin.

• Behind the pace: step the price down toward the floor, and use the hold or break-even decision in the mid-sellthrough section below.

The features page lists Sales rules and a Last sale rule type for speeding up slow-moving inventory.

The six-step OA playbook

1. Set a per-lot floor before the lot goes live. Calculate it from that lot's costs, or let Net Margin Repricing derive it from the cost you enter.

2. Filter the competitive set. Exclude sellers who are not real Buy Box competition, for example FBM sellers, sellers with feedback below 90% and sellers with only a few units left. Repricer.com's rule types include fulfilment method, feedback and stock level filters, plus an out of bounds rule that ignores rivals selling below your minimum.

3. Choose the rule type by seller count, using the table above.

4. Add a ceiling hunt where the listing is thin. Raise price in small steps (for example $0.25) while you hold the Buy Box, up to your ceiling. A static price misses the rise when other sellers' lots sell through.

5. Add a velocity trigger for slow lots. If sales fall behind your pace, step the price down by a fixed amount (for example $0.50) and reassess, never going below the floor.

6. Watch for competitor exits. When a major seller's stock drops sharply, their exit raises your Buy Box share. Check the Other Sellers view weekly for your top ASINs, or use the stock levels rule type, which prices up when rivals are out of stock.

Managing a large OA catalogue with variable buy costs

As the catalogue grows, floor accuracy becomes a systems problem. As a rough guide:

• Up to about 20 ASINs: update floors by hand after each sourcing session, before the lot ships to FBA.

• About 20 to 50 ASINs: use a bulk file. Repricer.com accepts CSV files with Min, Max and Cost prices, and its bulk actions set min and max ranges in one move. The risk is gaps: a lot that goes live before the upload sells at the old minimum.

• 50 or more ASINs: feed unit costs from your sourcing tool into Net Margin Repricing, so the floor follows the cost record rather than a manual update.

Setting minimum prices in Repricer.com for per-ASIN sourcing costs

Per-ASIN minimum price entry

In Repricer.com the minimum is set per ASIN or SKU. For each active arbitrage ASIN:

1. Calculate the floor with that ASIN's actual costs and enter it as the minimum.

2. Set the maximum (ceiling) from the highest Buy Box price in Keepa's 90-day history.

3. Choose the rule type from the seller-count bands in the playbook.

Bulk minimum price updates

Entering minimums one at a time gets slow. The integrations page lists CSV files with Min, Max and Cost prices, submitted through the API or via FTP. Build one row per new or updated ASIN with the calculated floor (the formula output, not a re-typed estimate), and upload as soon as costs are confirmed after a sourcing trip, before the units go on sale.

Keep each upload scoped to the ASINs that changed on that trip, and leave out any ASIN that runs on Net Margin Repricing, so a static number never overwrites a cost-driven floor.

Net Margin Repricing with per-ASIN cost inputs

Net Margin Repricing calculates the floor from cost inputs entered per ASIN instead of a typed number. Enter the sourcing cost and target margin. The floor is recalculated when an input changes, so an Amazon fee change does not leave a stale typed number behind, and a new lot at a different cost needs only an updated cost input. Net Margin Repricing is part of the Premium plan. The minimum and maximum price guide covers how floor and ceiling interact with rule type.

OAGenius and ArbitrageBoss cost data and Net Margin Repricing

OAGenius and ArbitrageBoss are sourcing tools that hold what each lot cost you, which is the exact input the floor needs. The integrations page lists both and says Repricer.com will automatically import unit costs from them. Net Margin Repricing then turns those costs into a floor.

1. Record the lot in OAGenius or ArbitrageBoss with its purchase price and associated costs.

2. The unit cost is imported into Repricer.com.

3. Net Margin Repricing calculates the floor from that cost and your target margin.

4. Check the new floor before the lot's first unit sells.

Two cautions. Include prep and inbound shipping in the cost you record, or add them in Repricer.com, so the floor covers the full landed cost. And when two lots of one ASIN overlap, check which cost the floor is using and use the higher one until the cheaper lot sells through. Without an integration, calculate the floor yourself and enter it before the lot reaches FBA.

Book a Demo to see per-ASIN floors, Net Margin Repricing and your sourcing tool's cost data working together for an arbitrage catalogue.

What to do when competitor prices fall below your floor

When a competitor's price falls below your minimum, Repricer.com holds at your floor and you lose the Buy Box to the lower price. That is the correct outcome. The out of bounds rule type is built for this: it ignores rivals selling below your minimum.

The decision not to follow

Lowering your floor to follow a competitor below break-even is selling at a loss. A suppressed Buy Box recovers when the competitor's stock runs out or they correct their pricing. A below-floor sale is permanent.

What typically happens

A competitor pricing below a sustainable floor is usually working from an incorrect floor of their own, or liquidating stock. Both tend to resolve in days or weeks. Hold your floor and resume rotation when they adjust.

When to investigate rather than hold

If your floor has sat well above the competitive range for more than 7 days, check three things:

• The lot's sourcing cost is too high for the market at your target margin. That is a sourcing problem, not a repricing one.

• The floor contains an error. Recalculate each component.

• The market has fallen below what is viable for FBA. Exit the ASIN.

The mid-sellthrough section below covers when the floor itself should change.

Using Safe Mode to test your minimums before going live

Safe Mode runs Repricer.com against your live listings and shows the prices it would have set, without changing any live price.

1. Enter the calculated floor for each active ASIN, and set the ceiling from Keepa's 90-day Buy Box high.

2. Set the rule type for each ASIN from the seller-count bands.

3. Enable Safe Mode on all repricing ASINs.

4. After 7 days, compare the simulated average selling price with your actual one from Seller Central Business Reports, at comparable Buy Box share.

5. Check the simulated prices. None should sit below the floor.

An ASIN that sits on its floor for most of the run is telling you the market price is close to your break-even. That is not a Safe Mode fault. Check whether the lot's cost is too high for the market.

If the simulated average selling price is higher than your actual one, go live. If it is lower, investigate first. Common causes in arbitrage are a minimum set too high, a ceiling below the current competitive price, and a rule type that does not suit the seller count.

Repricing after the floor is set

When to adjust your floor mid-sellthrough

A floor that was right at listing can become the reason units stop selling weeks later.

A seller buys 12 units at $7.25 with $0.35 prep, a $3.18 FBA fee, $0.45 inbound shipping, a 15% referral fee and a 20% target margin (illustrative figures). Floor = $11.23 divided by 0.65 = $17.28. The Buy Box price at listing is $18.99, and units sell.

Six weeks in, 9 units have sold at an average of $17.50 and 3 remain. Other sellers who bought the same clearance deal list at $15.99, then $15.49, then $14.99. At $17.28 the repricer sits above the market and sales stop. There are two options.

Hold the floor. The units are six weeks old, so the surcharge is far off, and prices often recover once the other sellers sell through. With no storage pressure, holding for two to four weeks is often right.

Drop to a break-even floor. If the units are nearing the surcharge, or you want to free FBA capacity, remove the target margin: break-even floor = $11.23 divided by (1 minus 0.15) = $13.22. At the $14.99 market price, a $13.22 minimum lets the remaining units sell for about $1.51 profit each instead of sitting while storage costs build.

The decision rule: if more than 90 days remain before day 181, hold at the target margin floor. Once you are within 90 days of it, switch to break-even to exit before the surcharge starts.

RA velocity repricing: price for BSR, protect the floor

For RA sellers, the trend in best seller rank (BSR) is a leading indicator. A falling BSR number means units are selling faster, so test upward toward the ceiling. A rising number means sales are slowing, so move toward the floor. RA sellers are clearing a finite lot, so for units past 90 days in FBA with a rising BSR, velocity matters more than margin. Configure the floor first, then layer the velocity trigger on top, so a fast BSR decline can never push the price below break-even.

The first 48 hours after going live

The first 48 hours of live repricing on a lot are the highest-risk window, because floor errors cost money immediately. Run these checks on live prices after your 7 days in Safe Mode.

Hour 12, hour 24 and hour 48 checks

Hour 12: price check. Pull the live price of each repriced ASIN from Seller Central and compare it with your calculated floor. If any ASIN is priced below its floor, the minimum was entered wrongly. Do not wait for hour 48. Correct the minimum and recalculate that floor now.

Hour 24: Featured Offer Percentage. In the Sales and Traffic by Child Item report in Business Reports, pull the Featured Offer (Buy Box) percentage per ASIN. Compare it with the share you would expect from the seller count, such as about one in two on a two-seller listing. Amazon does not split the Buy Box evenly, so treat that as a rough yardstick. A figure well below it suggests your price is above the competitive range.

Hour 48: average selling price. Pull the average selling price for the 48 hours and compare it with your floor and your Keepa ceiling. Close to the floor means the market sits near your minimum. Well above means the configuration is working.

Three signs your minimum price is wrong

A minimum price error is silent in the dashboard, because the repricer does what it is configured to do. Each sign below can be fixed without pausing repricing.

Sign 1: the repricer keeps hitting the floor while competitors seem to price normally. Your floor is above the competitive range, from a sourcing cost too high for the market, an FBA fee estimated above the actual, or a target margin the market will not support. Confirm the actual FBA fee and recalculate. If the corrected floor is still above the competitive range, the lot is not viable at your target margin. Hold the floor, and do not cut the margin target just to compete.

Sign 2: you win the Buy Box but revenue per unit is lower than expected. Your floor is below your true break-even, usually because prep cost is missing or the FBA fee was estimated too low. Recalculate with all-in costs and update the minimum. Then check how many units already sold below the corrected floor and count that against the lot's profit.

Sign 3: Buy Box share is below what the seller count suggests, but your price looks competitive. The rule type may not suit the competitive density, or the competitor filter is too narrow. With two or three sellers on a match or undercut rule, move to a ceiling hunt or position rule. If the filter reads "FBA only, 98%+ feedback", loosen it to 90% so relevant Buy Box competitors count.

Key Takeaways

• Arbitrage needs per-ASIN minimum prices, because sourcing cost, prep cost and inbound shipping vary by lot.

• The floor is (sourcing + prep + inbound shipping + FBA fee) divided by (1 minus referral rate minus target margin). An estimated FBA fee is the most common error.

• When two lots of one ASIN have different costs, use the higher lot's floor until per-lot floors are automated.

• Match the rule type to the FBA seller count: ceiling hunt for 1 to 2, position rule for 3 to 4, match for 5 or more. An undercut rule on a thin listing starts a spiral.

• Limited stock runs on a clock: the aged inventory surcharge starts at 181 days.

• OAGenius and ArbitrageBoss unit costs can be imported into Repricer.com, and Net Margin Repricing (Premium plan) turns them into a floor.

• Test in Safe Mode for 7 days, then check price at hour 12, Featured Offer Percentage at hour 24 and average selling price at hour 48.

Action Plan

1. List every active arbitrage ASIN and note the sourcing cost of its most expensive active lot.

2. Pull the FBA fee per ASIN from the Revenue Calculator, and confirm prep and inbound shipping.

3. Calculate each floor, using the higher lot's floor where lots overlap.

4. Count the active FBA sellers on each ASIN and choose the rule type from the bands.

5. Enter the floors as minimums, set ceilings from Keepa, and set up the cost import if you use OAGenius or ArbitrageBoss.

6. Run Safe Mode for 7 days, then compare simulated and actual average selling price.

7. For slow or ageing units, decide in advance whether to hold the target margin floor or switch to break-even as day 181 approaches.

8. Go live, run the hour 12, 24 and 48 checks, and recalculate any floor that fails.

Frequently Asked Questions

1. How do I set minimum prices for my Amazon arbitrage products?

Use the floor formula: (sourcing cost + prep cost + inbound shipping + FBA fee) divided by (1 minus referral fee rate minus target margin rate). Enter the result as the minimum per ASIN in Repricer.com, by manual entry, a CSV file or Net Margin Repricing. With $6.99 sourcing, $0.50 prep, $0.40 inbound, a $3.18 FBA fee, a 15% referral fee and a 20% margin, the floor is $11.07 divided by 0.65, or $17.04. If several lots are active at different costs, use the higher lot's floor.

2. Why am I selling below cost on my arbitrage products?

The usual cause is a minimum set below true break-even: variable per-lot sourcing cost, stale cost data, different prep requirements, different FBA fees across size tiers or omitted inbound shipping. Recalculate the floor for each lot and update the minimum. A competitor pricing below an otherwise correct floor is normal and is not a below-cost sale, because the repricer holds at your floor.

3. How do I connect OA sourcing costs to my minimum prices in Repricer.com?

The integrations page lists OAGenius and ArbitrageBoss and says Repricer.com will automatically import unit costs from both. Net Margin Repricing then calculates the floor from those costs and your target margin. Without an integrated tool, enter the landed cost for each lot directly or upload a CSV file with Min, Max and Cost prices, and check each new floor before the lot's first unit sells.

4. What repricing strategy works best for OA and RA sellers?

Match the rule type to the active FBA seller count on each ASIN: a ceiling hunt for 1 to 2 sellers, a position rule for 3 to 4 and match for 5 or more. Avoid undercut rules on thin listings. Whatever the rule, a correct per-ASIN floor is the lower bound, because an incorrect floor sells below cost under any rule type.

5. What makes OA repricing different from wholesale repricing?

OA buy costs vary by sourcing run, so the same ASIN needs a different minimum for each lot, while a wholesale seller has a fixed contract price and one floor per ASIN. OA lots are also smaller and run against the aged inventory surcharge clock, which starts at 181 days. OA repricing needs per-lot floors and velocity management. Wholesale leans on competitive positioning and ceiling capture.

Book a Demo to see per-ASIN floors, Net Margin Repricing and velocity rules configured together for an arbitrage catalogue. Or start your free trial with Safe Mode and enter your calculated floors for every arbitrage ASIN.