Buying iPad on Ebay?

Hi, Is it worth buying ipad air M2 on ebay? I see a lot of ipads with great prices comparing to the one on Apple website (Ipad Air M2 11", 128GB, wifi only, $600 without tax). How do I check if those ipads on ebay are "valid" ? And is 128GB enough for someone who plans to use it as an entertaiment?

Example attached