New x800 Pro's go for 150ish still, but for a card that old I am going to say my top price used might be around 70ish dollars.
The one you are prolly looking at on ebay is a monster card though (has VIVO and gdr3 memory on it.) Not a bad deal I guess.
Actually looks like there might be a chance you could snipe a great deal on the x800 type cards within the next day (prices are pretty low on em. That is if you are not in a hurry to buy one.