I've found a few used on ebay for $180 or so... seems like they're selling for more than that right now.
Not sure if I would be willing to trust a used card from ebay for 180. I feel like the chances of the card breaking are much higher. I would need an amazing deal to make me reconsider my stance.
Buying video cards off Ebay is a hit or miss, I bought several of my 5970's on Ebay and they all work but some of them have artifacts even on stock settings but they work for mining but for gaming forget about it, clear signs of over-heating.
So I don't know about the cards breaking down or failing but definitively you might get some that have artifacts.
Also most cards on Ebay, have no refunds / returns, so I am just glad when I get the card it works and is not a DOA.