First of all, a "crypto Ebay" would not be feeless. Handling with Bitcoin costs always fees.
Secondly, crypto Ebay's already exist in the Dark Web. There you can find many marketplaces and Ebay clones where you can buy all things and stuff (legal and illegal) with Bitcoin and cryptos like Monero.
I just meant feeless from the Ebay perspective. They charge huge ammounts of money to sell things. Crypto transactions can be tiny.
Like I said I don't want to use the darkweb. This isn't about doing something illegal it's about having a cheaper and more viable alternative to Ebay.