You're all forgetting that they're talking about 3 cores, not 3 cpu's. They are most likely using the same technology used in their power4 and power5 series of multicore processors.
Wether or not it will be to expensive, and hot can not be derived from the information divulged so far. You don't know how complex the cores are, there's no information about the manufacturing process, transisitor count, power consumption, detail size, etc etc.
As for utilization of multiple core, lets just say IBM has a bit of experience in this area.