FBA sellers often calculate margin off the wrong number, product cost alone, while Amazon’s fee structure quietly takes a much bigger bite than most sellers initially account for.
The full cost stack for an FBA product
- Product cost, manufacturing or wholesale
- Inbound shipping to Amazon’s warehouse
- Amazon referral fee, typically 8-15% of sale price depending on category
- FBA fulfillment fee, based on size and weight
- Storage fees, which increase seasonally and for slow-moving inventory
Why true margin often surprises sellers
A product that looks like it has a healthy 40% margin based on product cost alone can drop to 15-20% once referral fees, fulfillment fees, and storage are fully accounted for, and that’s before advertising spend, which many sellers track separately rather than folding into per-unit margin.
A more honest way to calculate it
Build every fee into your per-unit cost basis before calculating margin, not just at month-end reconciliation, since pricing decisions made off an incomplete cost picture consistently underprice the actual product.