In general, faster processors result in a higher price per unit of performance . This is shown in the graph below of different 32-bit systems. As the performance improves, the frames per second bought by one U.S. dollar decreases:
Because the 64-bit processor represents a greater change than the ever-frequent increase in transistor number per microprocessor (as is the case for increasing performance on 32-bit machines), they offer a unique opportunity to buy performance cheaply. The cost of 64-bit processors is not significantly different than that of their 32-bit predecessors, while for certain applications the performance can nearly double. Thus, the cost per unit of performance could decrease dramatically with 64-bit processors!