I learned how to tune on my own cars, and branched out to helping out friends. Hundreds of hours of researching, learning, experimenting and there is always more to know and things that are changing. So many things are platform specific and to be a very good tuner you have to know your platform inside out (which is why I only tune a handful of platforms these days). After about 8 years of learning I opened my own shop and have been doing that for about 5 years now.
As time has gone on I am much less tolerant of what I will actually tune / attempt to tune. Ive had this discussion with quite a few local tuners and its always the same thing. Almost every problem with tuning a car stems from a mechanical problem.
I tier my tuning prices to be more inline with the actual work performed and licensing costs in the case of things like Neptune chip tuning for hondas, or Nistune for nissans.
For example, basic setups on opensource are 200/350. Cobb AP Tunes which Ill be doing shortly will be slightly more. Standalones start at 850.
Im always willing to answer SPECIFIC questions that anyone asks regarding tuning theory. I wont sit down and walk you through tuning a car, but if you want to know what table X does, Ill always explain it.