Free tool
Referral fees move the contribution line, not the vanity ROAS.
A 15% referral fee on a low-ticket item can erase the unit. Compute fee dollars from basis points without floating point.
Fee dollars$3.75
Remainder after COGS & other$0.34
Formula
fee = sale × bps / 10000 (half away from zero)
Example
Headlamp Pro $24.99 at 33.61% referral is $8.40 before FBA — enough to go negative with $14.80 COGS.