The amount that maintains that 10,000 rounds, if that is their goal.
When Kemper Lakes 1st opened, they were formualting the greens fee. They figured x number of rounds at $20 would achieve their goals. My father thought that would be too much wear and tear on the new course and suggested the steep price of $25/round. His logic was they wouldn't lose 20% of X players and they could spread out the tee times from 8 to 10 minutes. It worked and they actually made more money that 1st year AND had a bigger reserve for maintenance/repairs.
John, I think it is hard to come up with a number if you don't know more aspects of current expenses and the owners goals.