Here are the guys who machined my 1-3/8" shafts last season. They did a nice job and they were very careful about everything. I had to pay in advance to obtain the 1-3/8" stock, which I didn't mind. I had to take my old shaft in for them to look at in order to assure the new ones would be the same. I also had to go back to get the new shafts. While this wasn't all that much of a hassle, it did consume valuable time and some gas money too.
This shop produces prop shafts from time to time, but they sure don't do it as a routine. There is something to be said about shops with modern CNC equipment that can work to digital precision on a routine everyday basis. In the end both alternatives are viable. Shafts have been made this way for a long time and they give years of service. We're lucky to have alternatives now days.
Regards, Paul