As a 4 time Grand Prix Rider of the Year, I give many clinics throughout the year.
I expect the hosting stable to make a profit for the use of their facility. Many clinicians charge more than I do. A typical clinic day for me, is 4 or 5 groups with 3-4 people per group. That way I can spend enough time with each rider. Most stables charge about $300 per rider for 1 of my 2 day clinics.
And when are you coming next to Massachusetts? :-)