I flight instruct at a university aviation program. Our CFI's are paid on a graduated scale.
You start at $8.50 an hour.
You get a $1 raise for each of the following:
100 Dual Given, 300 Dual Given, 500 Dual Given, 800 Dual Given, 1000 Dual Given
Bachelor's Degree, Master's Degree
You can top out at $17.50. The instructor fee is $25 an hour.
That fee also goes to pay dispatchers, line service guys, maintenance, and Check Instructor salaries. Check Instructors are salaried at around $20,000/yr.