In terms of overall performance, the top of the line Intel quads kick the shit out of AMD's top line offering. However, in terms of price, AMD isn't that bad. The AMD 9950BE goes at $235, and the Intel QX9775 is $1,550, almost 7x the price. Even if performance is over that ratio (I don't think it is however), most people don't need to calculate pi to 1 billion places in under 10 seconds. Besides, other hardware is much more the limiting factor (hard drives, memory, video) to performance.
Sure, you get what you pay for, but even similarly performing intel's proc price is slightly higher.