At the time I had the action job done, around 2000, it cost me $125. I'm sure it would be more now, but in my opinion, it was worth it. Very smooth cocking action, the forcing cone cut really improved accuracy, and he even cut a few small grooves in the cylinder pin to help hold lube. Made a difference.
If I was going to have someone do it now, I would have Jay Strite at Kirst Konverters do it. I have read that he does excellent work. He does more than just installing conversion cylinders: http://www.kirstkonverter.com/custom-gunsmithing.html
Here are some pics of my Shooters Model: