New Amazon Seller Question – Calculating Profit with FBA

Hey Amazon sellers, I could use some guidance. Suppose I bought a hat for $10, and its listed on Amazon for $20, and used the FBA method. With Amazon fees at $2.50 and referral fees at $1.00, would my total profit be $16.50, resulting in a $6.50 profit? Is that how it works?

Are there any other fees I should be aware of when using FBA? Appreciate any insights or advice you can share! Thanks a bunch!