For one, this should have been posted in PC Steals and Deals. And two, this is probably just a P4 Northwood with suffecient cooling (actually, it would need a lot) that is oc'd to 3ghz. But, I really dont think so. Those guys are probably just tryin' to rip you off.
This will all be over before you can say Cat in a Hat.
Sounds shoddy and possibly illegal to advertise that online without stating that the CPU is overclocked. Sounds like these people are tryin to take you for a ride...