Another perspective on CPU value
 

As you might have already seen, the value section of our grand Athlon II vs. Core i3 showdown article includes performance-per-dollar graphs based on whole system prices. We began including these numbers some time ago at the behest of a readers who rightfully feel that, if they need to buy a whole PC to begin with, then processor pricing is only part of the equation. For example, if processor A costs $200 and only performs 50% better than processor B, which is priced at $100, then the prospect of paying double for 50% extra performance may not seem that worthwhile. In a $900 system, however, paying an extra $100 for 50% of extra performance suddenly becomes far more enticing.

http://techreport.com/discussions.x/18502