I have refrained from joining this conversation until now. For the record, I have completed the Master Gardener course here in Nebraska. Here we did have to pay a tuition to help pay for the informational books and materials. It is truly a beginner's course of study with a broad overview. It would be very difficult to learn and retain the vast amount of information in what for us was an 18 week, four hours per session once per week course.
Our instructors were PhD Extension and University of Nebraska instructors. Each had their own expertise. At the time I had been gardening for forty years and it is amazing how much new, up to date material there was. And how much more in depth each section needed to go into for the kind of Master Gardener imafan26 would like to see. Perhaps it is the name (Master Gardener) that is in error.
For ten years I have kept up with additional instruction and have done the volunteer hours to remain active. Of the class I was part of only maybe 4 of the thirty students have remained active. Maybe we took Intro to Master Gardening and there should be advanced groups with more advanced names. Not many would continue past the beginner stage. For me it is a hobby rather than a career. I garden, give informational talks and seminars and write a gardening column for the local newspaper. I also take calls from the public for advise. I DO NOT know a lot of the answers, but I can find the information to get people headed in the right direction. That to me is the reason for the Master Gardening course of study.
Those folks with years of book study, field research experience and practical gardening (horticultural) experience are my back-up. I figure myself as a conduit to and from these people for answers more complex than what I know. Most questions are pretty basic and I can be of service, but some are out of my range.