I used to teach orchestra. My two sisters and a brother in law do teach. As far as I know, none of them are making a fortune. I certainly did not.
Being a music teacher sometimes gives you the opportunity to witness others do what you do for a living. I must say that in the music world, there are teachers out there who really have no clue how to get their students to succeed. I do not know the reason -- if it is a lack of knowledge, enthusiasm, drive or whatever. I have witnessed teachers telling students ways to do things in a manner that does more harm than good, and not willing to consider other techniques that might help them be more efficient in the classroom. I have witnessed teachers being completely happy with a poor effort from their students. Successful teachers make an effort to try different things, work with as many students as they can, and not give up when a student just doesn't understand. A battle has to be made between the teacher and ignorance. Many teachers after a few years are happy letting ingnorance win.
My point.... A warm body can complete the requirements to become a teacher, but not everyone has the skills or passion to be a good teacher. Unfortunately, those that do are a rare breed these days.