The difference between the 460 and the 5850 is just a few fps. Even closer when you consider minimum frame rate. (The 460 actually wins a benchmark there).
The 5850 needs to drop down to $199 to be competitive with the 460.
The 460 is a great bang for the buck card. For this game, with AA, the 460 is a better choice than the 5850. The 5850 is faster overall, but I don't think it's advantage is enough to justify it's price difference.
But, the pretty much the same can be said about the 480 and the 5870. The 5870 will give you an identical experience in this game as the more expensive, louder, more power hungry 480.
Even the premium 5970 actually delivers more frames per dollar than the 480. You don't often see that from ultra highend cards.
I guess what you could say is that, going strictly by this bench, there are some winners and losers.
Winner: GTX460 - Almost as fast as the more expensive 5850.
Loser 5850 - Too much of a premium over the 460 for it's very moderate performance edge.
Winner - 5870 - Very nearly as fast as the more expensive, hotter, more power hunger 480.
Loser - GTX480 - All those negatives for not tangible difference over the 5870.
Winner - 5970 - Nothing else is even close.
Loser - Nvidia? Despite coming out months later they can't match this card. Of course when we start looking at multiple cards things get thrown up on the air. But for a single card solution, the 5970 is the king by a decent margin.