You are paying fees for several reasons.
When you list you are charged a listing fee. We get 50 'free' listing fees.
More than 50 and the basic charge is 30 cents each.
When we sell we are charged a percentage of the selling price (10% usually) and a percentage of the shipping fee (10% again usually).
These are put on our monthly invoice.
We are notified of the total monthly and the total fees are collected about 15 days later.
We are also charged 30 cents or 2.9% by Paypal for processing customer payments.