Wouldn't this be violating copyrights left and right? Presumably most of these listings have pictures and I'd be surprised if Amazon were asking permission to reproduce them. Would the same apply to item descriptions...?
The first sale doctrine allows for public of owned works for the purpose of sale. Otherwise eBay, used book store, and flea markets would all be massively violating copyright.
Moreover, I'm pretty sure purchasing a product does not give you the rights to use all the marketing materials for that product. Those copyrights are separate.
And the act of listing inherently happens before any purchase.