The problem is not in your rate, but in your way of thinking on this as you are factoring in emotion. Actual operating cost for a tractor is no where near $75 an hour; here in Maine it is calculated at $37.50 an hour with an operator getting $18 an hour. Those are not my calculations, but by people who calculate in both the obvious and hidden costs too. (My calculations show the rate would be $56 an hour not including a transportation fee).
That may seem low, but you are basing your rate on FEAR and not solid averaging. Yes, it is possible that damage to your tractor may occur while working it on a job, but that is fear; averaged out over several jobs a tractor will not sustain a lot of damage, and that is where the money is made.
Fear is emotion, and if a tractor owner cannot pull that out of the cost, then they are going to price themselves out of a lot of jobs too. For me that is fine, I did not buy a tractor to work on other people's projects, I got all I can do on my own farm. But if a person buys a tractor intending to do custom work, they MUST understand the difference between the Law of Big Numbers (averaging) and emotional attachment.