New from Ford Racing, they are about $16k. There is a motor and 6spd trans on eBay right now for $12k (see link below). I have heard of people selling them from closer to $7500-$8000. Pricey for sure, but no more than the 2003 cobra motors were when they were a year or two old. They will come down to earth.

MUSTANG ENGINE SHELBY GT 500 COBRA 5.4 & TRANS T6060 : eBay Motors (item 330403884114 end time Feb-20-10 17:25:44 PST)

Brian
EFI-Unlimited