And by "affordable", they don't mean "cheap piece of crap". They mean (or at least claim) "bang for your buck" for the serious gamer on a budget.
Nvidia today took the wraps off the GeForce GTX 460, designed to be the the company's first real mass-market card built to support DirectX 11. Priced at $199, Nvidia reckon that the GTX 460 is in some areas (like tesselation, a new DX11 feature) up to four times faster than equivalent ATI cards.
Early benchmarks suggest it comes close in performance to a range of more expensive cards, though whether it comes close enough to make it a more worthwhile purchase for the thrifty consumer than, say, the cheaper ATI Radeon HD 5770 (at $150) is up in the air.
Still, it's always nice when previously unaffordable (for the masses) tech becomes...slightly less unaffordable, so if you're in the market for something to run DirectX 11 and couldn't quite justify spending $300+ on a card, this might be something to look into.
Not sure what DirectX11 even is, let alone what it brings to the table for PC gamers? You might want to consult this handy guide!