Depends greatly on where you are located and the competition.
My friend charges $75/hour for his skid steer clearing commercial properties.
I'd say look at your costs to operate and add your profit to that number. Then look at your competition's pricing. Figure out how to differentiate your service from theirs. What advantages do you have to offer?
Don't forget to include wear and tear on your machine as well as maintenance.
If you are breaking even with costs, you are really losing money.
A "fair rate" is defined by what the market will bear.
Good luck and have fun!