I wondered about the same thing. I would take a WAG(wild *** guess) and say a used PCM (Powertrain Control Modual) would run about 250.00 to 400.00.
but im thinking that the problem comes in with the VIN number. I THINK (strees think)every PCM is encoded with the car''* VIN and it does a "vin check" at startup with the BCM (body control module), Radio, and some other stuff. All of this stuff is done to fight Hack shops selling out stolen parts.
im in the same boat as you
A:ASE chip 350.00
used PCM =$300.00
GM Tech 2 to reprogram the PCM= $3000.00
the balls to F*ck with your PCM while still under warntee= priceless
the other alterntave
ase chip= 350.00
rental car for a week= 250.00
good luck in whater path you decide, but let us know.