How about a good say call it a "Work-out Area"...Driving range, putting green, and chipping area? You could set it up in either a "bucket of balls", a time element thing, or a choice of either.
Bucket of Balls: I'd pay say 10c for a 200 ball bucket. Then once the bucket is bought it stays in your account until the bucket is empty.
The Time Element: I pay say 10c for an hour in the "Work-out area". That too could stay in your account until the entire hour is used.
Food for thought gentlemen and have a super day!