Doesn't have to be a bit coin auction site though. Those are ebay fees and how they make their money even if they accepted BTC it would still be the same.
Yup, ebay hosts the auction for you and makes their money off of FEES.
Frankly, sometimes it is worth it seeing as how much time spent/lost on trying to sell local or on other websites. At least with ebay you can reach a larger audience and simply sell your item and not let the fee weigh down the time you saved.