That's interesting, and actually by far the worst I've seen a GTX460 in testing vs. 5850. I'm not gonna call bias, but compare to Anand test :
http://www.anandtech.com/show/3809/nvidias-geforce-gtx-460-the-200-king/18
Unoverclocked, stock 1GB GTX460 (not overpriced Asus TOP card) is very close to stock 5850 performance. Once overclocked, it's solidly between HD5850 and HD5870 stock performance. Yes, you can also overclock 5850s as well, and probably beyond the reasonable range for a GTX460 to match, but the price difference is definitely there.
The article brings up a kind of apples/oranges comparison too, by mentioning rebates on one card but not the other. The 5850 is a great card, but it's soon EOL and it's still a noticeable amount more expensive unless someone flat out overpays for the 460.