Now I know, not everyone who is mining bought new hardware to mine with. But really, you only have to look at ebay to see proof that mining really IS having a big effect on ATI video card prices. There are far better gaming cards than the 5870 out there, and yet, the 5870 is selling for much more than them on ebay. What other explanation could there be other than miners are buying them up so fast as to actually affect the price point (which you claim isn't possible)?
Sure, mining is affecting *certain* video card prices. All of which are essentially out of production (except the Sapphire Xtreme series, AFAIK). You have a situation were free money (or at least extremely optimistic money) is chasing an extremely limited supply. Not too much unlike what created the housing bubble.
I agree with you that it is in fact affecting prices for the higher end of the 5xxx line. That said, I do not *currently* see it affecting the 6xxx line at all, and I doubt it will until the 6xxx line goes out of production and inventories have been depleted.