If you go to My eBay > Account, you can check an itemised list of all the fees eBay have charged to your account. The first 40 listings of any given month should be free, but you will still be charged for any upgrades, extra categories etc, plus a final value fee (9.9% of the sale price) on any item that sells.

On my account, eBay also shows me a total for how much money I've saved by taking advantage of their promotions, so if for example my fees are $15 and the promotional savings were $10, it's their way of saying "we could have charged you $25 for all this". 😄