It sounds like you may be wondering if you are getting under paid. I have seen spin instructors making as little as 12.50 an hour to as much as 35.00 an hour. It depended on the gym (rec center vs. club vs. high end club) and the experience of the instructor as well as their class size. I personally would expect to be paid at least 25% of the class gross at a club. It really doesn’t matter what anyone in the area makes, I know I deliver a top level class with great energy and high safety awareness.
But if it is important to that you know your area average, try the fitness chat/blog on craigslist for Chicago. Or if you are fearless and freindly, attend some area classes and ask the instructor what they are getting per hour/class. I like to attend other instructors classes just to see what everyone is doing. And I am not above learning something new from even the greenest of instructors.