I think besides the economy the another part of the problem is chips have become so fast increases in performance are not noticeable by the average user. Companies especially Apple kept creating background crap/apps to try and chew up some CPU cycle to create a need for more powerful chips, but the chips are handling it all just fine. The only people really benefiting are people working in production level video. Even people working in audio the faster chips are of little benefit. I think this is why Apple is finally trying to get into the game market. Hardcore gamers want and are willing to spend money on bleeding edge tech so Apple needs a presence in that market to sell its next generation chips.
So selling more powerful chips are becoming harder sell.