It depends if you are independent or working for a corporation. It will vary. If you are independent, then your potential income is unlimited. However, take that with a grain of salt, as you are fully responsible for your own clients and class attendance, which may vary depending on your reputation in your local community. You may also be responsible for gym rental expenses as an independent.
If you are working for a fitness corporation or gym owner, then you will more than likely be capped at a certain $ amount. The corporation takes a percentage of revenue of the classes as a profit (that is usually very much in their favor) and then obviously has to pay the government a percentage for taxes. After that, you receive your net income. Unless you work as a contractor, then you have to keep track of your own taxes.
At higher end clubs, which is where I use to work, you could probably expect anywhere from $30-$75 per hour.
This was just from my experiences working as a bootcamp instructor in different clubs and various locations.
Hope this helps!
Body Transformation Instructor
NASM-CPT, AED, CPR