all the others are right on. The thing to add is also the environment in which this instructor teaches. I teach at a large facility, and Pilates instructors get as much (or little as the case may be) per class as all the others. At a studio in a small group or one-on one setting, this can look quite different. Depending on the arrangement between the club/studio and the instructor, there is also usually a discrepancy between the money the client is charged and what the instructor gets.
Pilates, of course, lends itself to in-home training of clients many of whom may have some equipment, and here the rates can be different yet again.