Left me put some meat on the bone of my dead ducks statement.
The 6600GT is faster than the 9800 and 59xx series graphics cards and being made on the cheap 0.11 micron process will be cheaper to build and cheaper to buy.
Take the Subaru analogy ( ignoring looks as this is of little importance for the video card buyer )
Subaru 5900 200bhp and costs £20k
Subaru 6600GT 240bhp and costs £19k
Now sales of the first to the latter ? You could say that you could make the former cheaper, but it has an expensive build so your margin is less. Better to buy the new Subaru 6400 which is even cheaper still and just about matches performance.