With over 13,000 employees at eBay, I'm sure they are aware of crypto.  If there was an advantage to their current model to use crypto they would have implemented it already.  And like the previous poster wrote, there are still fees with crypto, and the company needs to make a profit.

I don't think any developer here would spend thousands of hours making an eBay clone if they couldn't charge fees, and the instant it started making money, eBay could add it on easily.

What you want is an auction site that doesn't need to refund/return.