Yup, it's too expensive for all but the Gulf Stream corporate big wigs, these days. Haven't lifted any gear in many years. I have a few friends who still fly and that's about it. (My wife would say-He just likes to talk).
As to your purchase of the tooling, I have done the same thing more than once or thrice and in most all of the cases, I came out when I used the tooling and the rigging the second and third time (and in a case or two, even more times). I usually learned something in the process which unfortunately once or twice was that maybe I had have been better off...
I seems that most CNC machining of gears involves hobs or high speed single point profile cutters. Perhaps an up to date machinist would comment on this, I would welcome that. There is a guy down near Tampa, FL that makes replacement gears for Atlas/Clausing on CNC. I don't know what type of machine or tooling he uses, but he has the components programmed and just sets up the blank, zeros the tooling, and turns the machine loose. I'm not sure if he makes any other replacement gears for different lathes. Atlas/Clausing/Craftsman used die cast and "Zamak" (crapalloy) powder metal gears and levers, etc.
Your Model 1875 must be one of the later production machines considering that the back gear engagement is different from the one I have; I have not seen a Logan like yours. I think most South Bend lathes in our size machine used a set up similar to your Logan.
I think that your approach is solid. You may want to slow cool the gear after brazing in lime to prevent distortion. There have been, from time to time, some decent prices on gear cutters on ebay. I think you did fine considering that new DP cutters are running from about $50 and way on up in price. Good luck, Geoff