Currently there is a massive amount of competition in almost every corner of the computer industry. This has resulted in a wide range of products, as manufacturers attempt to capture as much market segment as they possibly can. Take the war between ATI and Nvidia, for example. Each company has been scrambling to gain an upper hand in every price bracket. Currently there are loads of options in the sub $100 range, $150, $200, $250, $300, and all the way through to $600+. The same can be said about CPUs, which have not only reached phenomenal levels of performance, but are also more affordable than ever.
For cheap gaming, AM2 is definitely the way to go as there seems to me much more selection. You can see what Tech Spot recommends.