600$ vs 649$ is a "fair" comparison IMO. If not unfair considering the extra 50$ you have to pay for a single 280.
Anandtech shows it vs GTX 280 SLI anyway. The nvidia cards win in Crysis, Quakewars, Assasins Creed and Oblivion. The 4870's beat 2 x GTX280's in COD4, The witcher and Bioshock. For 1300$ the two GTX 280's should've wiped the floor with the ATI's in any game.
Actually the only game it really wins in is Bioshock and CoD4 (by about 10 frames). In the witcher 4850CF wins by 1.1 frames which is within any margin of error.
But then there is stuff like this where 4870 is just stomped:
QX9770@3.66Ghz 24/7 365
790i STriker II Extreme Rock Solid Stable (finally)
8GB Corsair XMB 1600Mhz DDR3
MSI 280GTX OC 650/2300 in SLI
300GB Velociraptor, 500GB Data
4X Liteon Blu-ray Burner MMORPG
Vista 64
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