I think it depends on a lot of factors. I'm teaching a class to friends and am only asking $10 a person to cover workbooks and samples - but I got a great deal on a room and am doing it more for fun. If I continue this class monthly or even bi-weekly I may have to up the cost. Now, I taught a paper piecing class at a local quilt shop at the fee was $20 per person plus they had to buy the pattern and materials. Half of that class fee went to me and the other half to the shop owner. Another was a hand quilting class and the fee was $15. NOW - I took an applique class at the library and it was $3 per person. SO - fees vary depending on what the class involves, what materials will be needed to run the class, and how much overhead has to be balanced out. Obviously I can charge a lot less teaching on my own than at a quilt shop because I don't have to make money for the shop! But when I rent a room to teach I have to cover the cost of the room and supplies to teach and if I want to make something hourly I have to figure that in too. If fees get to extravagant it deters people from attending.
Not an easy question to answer here!
Good luck to you!