I have taken a intermediate course sponsored by my company. I don't really know how much they charged the company. However, a friend of mine took a course also, and she paid about $92 for 2 one-hour sessions. This is a new york city price. My suggestion is to find out about how much the knitting classes charge around your area and charge according to the range.
The beginner class I had visited was to do a project of a scarf with 4 different patterns. Each pattern took a session. The intermediat course was also 4 sessions; project was a cable hat (I posted a photo last month). Skill learned each course was not divided as obvious as the beginner's classes.
I hope this helps. Good luck.