Amazon FBA looks like a simple business until you actually price the SKU. List price minus cost of goods is the calculation most new sellers use, and it's the reason most new sellers go broke. Real FBA economics are a stack of fees that each look small in isolation and collectively eat 35–55% of the sale price.
The fee stack on a single unit
For a $25 product weighing 12 oz in the standard-size tier, expect roughly:
- Referral fee (~15%): $3.75 — Amazon's cut on every sale.
- FBA fulfillment fee: $4.75 – $5.50 — picking, packing, shipping.
- Storage fees: $0.20 – $0.60/unit/month, more in Q4.
- Returns processing: ~5–10% of units, with the full FBA fee charged again.
- Inbound shipping to Amazon: $0.40 – $1.20 per unit.
- Advertising (PPC): often 8–15% of revenue.
- Long-term storage surcharge: if inventory sits past 271 days.
That's roughly $9.50 – $12 of fees on a $25 sale before you've paid for the product itself. If COGS is $5, your contribution is $7.50 – $10.50, not $20. Run the full stack in our Amazon FBA profit calculator.
The four fees that wreck unprepared sellers
- Q4 storage surcharges. Storage fees roughly triple from October through December. Sellers who stock heavily for holiday and don't sell through can end up paying more in storage than they earned in margin.
- Returns. Apparel, beauty, and electronics see 15–25% return rates. Each returned unit costs the inbound shipping, the original FBA fee, and often a return processing fee — and the unit may not be resellable.
- PPC tax. New SKUs can't rank without ads. The first 90 days of PPC often run at 25–40% of revenue, not 8–15%. Build that into the launch budget.
- Reimbursable losses. Amazon loses, damages, or mis-categorizes inventory at predictable rates. You can recover most of it, but only if you actively file claims — set up a recurring reconciliation.
The honest contribution-margin model
For each SKU, calculate three numbers:
- Gross margin per unit: Price − COGS − inbound shipping.
- Contribution margin per unit: Gross margin − referral fee − FBA fee − storage − returns allocation.
- Net margin per unit: Contribution margin − advertising − overhead allocation.
If net margin is below 15% of the sell price, you don't have a real business — you have a pipeline that converts cash into Amazon fees. Aim for 20–30% net at steady state, with a launch period that runs lower while you build reviews and rank.
Why "raise the price" isn't always the answer
Pricing on Amazon is enforced by the algorithm. Move too far above category norms and your conversion rate drops, your ad spend rises to compensate, and net margin collapses. The lever that usually moves more is cost of goods — supplier negotiation, packaging redesign, dimensional weight optimization (smaller boxes drop you into a cheaper FBA tier).
The takeaway
Don't model FBA on a back-of-the-envelope. Build the full stack with realistic return rates, holiday storage, and ad spend at launch-level rates. The SKUs that pass that test are the ones worth the inventory commitment. The ones that only pencil with optimistic assumptions are the ones that quietly bleed.