When registering a model, you must determine a sales value. This is the exact amount you will receive at the end of the kit, so there is no need to make calculations over fees. You just won't receive the amount determined in the crowdfunding's register, in case you don't collect enough, but, even so, you decide to take the project forward. When withdrawing, PayPal charges specific fees to make your withdrawal if you do not have a TED option available. To learn more about the withdrawal, check the fees directly with PayPal.