Transmission rebuilds/upgrades can run pretty high.
Here is Willwren'* Thread on his rebuild: http://www.bonnevilleclub.com/forum/...t=transmission
My rebuild is about to be finished up. Last fix is going in tonight or tomorrow (trans lines need to be changed out). Mine is running me 1845 in the end for parts and WAY discounted labor. I had a complete rebuild with all internals replaced, heavy duty torque converter (kept stock stall incidently), rebuild differential (No LSD), and all solenoids/wiring replaced, and a complete Transgo shift kit with all options. I'm pretty sure the total would've been more then 2700 without the major "My daughter was the maid of honor at your wedding" discounts.
Another option is this company: http://www.importperformancetrans.com/gmautofwd.shtml
I visited thier shop as its not too far from me. Pretty impressive operation. Incidently, they use the Limited Slip Differential from this guy: http://www.engineered.net