Ebay's policies are pretty clear if you take the time to read them. There are insertion fees whether the item sells or not. Fixed price and buy it now items still incur fees.
.Listing your items in multiple categories means Ebay can charge insertion fees for every category you've listed your item in. "Good 'Til Canceled" listings have recurring fees until you cancel them. There are a dizzying number of upgrades to that option that would add to a seller's bill.
"The fees for listing an item depend on the price, format and category you choose, and whether you add any optional listing upgrades."
"You may be charged final value fees if you violate our policy of buying or selling outside of eBay, or we may apply additional final value fees if you are not meeting our performance expectations."
It was your responsibility to read Ebay's policies before selling with them. I'm guessing if you read carefully the policy now, you will be able to understand what their charges are.
Ebay provides a wide audience for the seller of an item, and charges a good amount of money for that option. In addition to that, the seller is also paying Paypal and credit card processing fees to get the money owed them. It would seem like it's hardly worth the money...except that there's millions more seeing your ad than the people on the local social media market page.
Looking at Ebay's policies and fees, and the fees involved in payment processing, it's quite possible to operate at a loss.