But how much does a 939 X2 4800 cost today compared to an AM2 X2 4800? What about 6 months from now when AM2+ is the hot thing. What about a year and a half from now when he finally decides to upgrade? At some point it will be cheaper to buy an entirely new platform.
The market is dry enough as it is, unless you're sourcing parts from ebay or something. Personally, I've never been a fan of that since you never know what you're getting (i.e., is the chip working, has it been overclocked/overvolted in the past and appears to work but has intermittent problems, etc).