Short answer
The quick math
There is no universal lowest-fee marketplace because shipping, category, buyer-paid tax, boost fees, item price, and pickup versus shipping all change the math. Use one item price and cost basis across every platform, then compare take-home rather than headline percent.
Assumptions used
- Same item price across platforms
- Same item cost basis
- Buyer-paid shipping entered consistently
- Optional ads or boosts turned on only when they apply
- Platform schedules vary by category, country, and account status
Use it before you decide
- Enter one sale price, shipping amount, sales-tax estimate, and item cost.
- Run the comparison once with optional ad/boost fees off.
- Run it again with the ad or boost settings you actually plan to use.
- List where take-home and buyer demand make sense together.