Amazon FBA math can look simple until fee layers start stacking together. Referral percentage, size tier, product cost, and shipping-to-Amazon costs can quickly change whether an item is healthy or barely viable.
That is why seller research should focus on net profit after fees rather than headline revenue or markup alone.
Referral Fee vs Fulfillment Fee
Referral fee is usually a percentage of the sale price tied to category assumptions. Fulfillment fee is a logistics-style charge that depends heavily on size tier and weight.
- Referral fee changes with category
- Fulfillment fee changes with package profile
- Both matter, but the seller controls them differently
Why Size Tier Matters More Than Many New Sellers Expect
A product with a slightly worse package profile can move into a higher FBA fee band and erase much of the expected profit. Packaging and product dimensions are not just logistics details. They are profitability variables.
The Cost Stack To Watch
A more realistic profitability view includes product cost, shipping to Amazon, referral fee, fulfillment fee, and any other recurring selling cost you expect to absorb.
- Product sourcing cost
- Inbound shipping or prep cost
- Amazon referral fee
- Amazon fulfillment fee
- Ad spend, returns, and storage as separate realities to model afterward