Rates are too variable to make any assumptions. One operator could quote $1500 an hour because he is desperate to get work and does not bother with trivia such as maintenance reserves (or paying staff, or bills). He will do it for fuel and some - any - contribution towards the monthly lease. His business plan is in tatters already so if he personally pockets $100 out of it he will take the job. Another, who runs a proper business, could quote $3500 for the same job and might make $500 genuine profit after he has wisely put some aside for maintenance reserves.
The first guy might get that job and a few others in the short term, but will fold soon enough - leaving the market to the second guy.
Then there are long-term contract rates which could be anywhere between the above figures. Also variable dependant upon annual utilisation.
Best way to get a feel would be to pretend to be interested in a charter for a glee club or choir group or any other bull**** reason and get some quotes. But don't use those as a guide to what it really costs to run a King Air. It costs heaps.