7 series haven't sold at the $300 since summer of 06. If you bought a 7600GT AGP at Circuit City or BestBuy and paid full retail + 20% + extended warranty -- well, sorry. Unless by 'not long ago' you mean over 2 years -- 2 + years is forever in computer hardware terms.
9600GT and 8800GS can be had for a hair over $120 online. Midrange video cards don't drop below $100 until they're 2-3 generations old and worse than current generation low end, typically. How cheap do you want to see them?
People on ebay tend to bid up useless stuff to insane levels. Enthusiasts are more in the know, and are less likely to pay top dollar for junk. I'd say ebay.