Wages
I know the feeling.
There's too many instructors out there who are willing to fly for peanuts. They think their helping GA but in reality their just killing the industry.
I work full time for a flying school and get about £12000 a year. If I instruct outside of normal school hours I charge £35/per hour - and I always make sure I get it! It makes quite a difference to the bank balance.
My advice to all poorly paid instructors - Don't be worried about asking for more money, you've earned it. If the school won't pay it go somewhere else.
Nuff said.