It's really a YMMV situation. I'm a gamer, so dropping $220 on my 6950 was no big deal, and the fact that I can use it to more than pay for the electricity that my whole system is using makes for a nice bonus.
It's not that unusual to find overpriced used merchandise of any sort... people always think their crap is worth its weight in gold. Craigslist and ebay are the best places to find items like that.
"Thanks, Matthew, but I have several people willing to pay $350."
Ok... then why did he still have the card?