That link shows the 660 TI being $309. The 7970 will be a faster card, and it costs $100 more.
I caught that too, but I'm thinking the OP meant these two cards
in which case the price difference is $60.
The problem is that you're trying to compare AMD's fastest GPU, the 7970 (7990 doesn't really count since they're never in stock) against Nvidia's 4th fastest GPU behind the GTX 690, 680 & 670. It's no comparison.