Good luck returning a used card, which is what we were talking about, to a seller that knew it was bad from the start. Everybody talks about how great Ebay's protection policy is but the fact is, it's really not. I know a few people who have tried this and in every case they could not prove to Ebay that the card was not faulty when they received it. The seller disputed it, they were out their money. Simple as that.
And that's without even factoring in the well known fact that there are MANY hacked Ebay accounts selling fake or faulty products and there's NO chance of getting anything back from one of those.
If you bought the card from a reputable seller who has a good reputation, and wishes to continue doing so because that is what they do, then sure, they're not going to damage their reputation by not playing ball because a lot of those seller have likely bought batches of product and hardware and have no idea the product has a problem. But that's going to be a crapshoot as to which kind of seller you end up dealing with.