One of the private clubs I know charges a nominal fee (you can bring guests, too) mostly so, as they told me once, people stopped booking times and flaking out. They were finding that Mr. Smith would book the time, blocking the time from being used by someone else, and then wouldn't show up half the time.
If you can get away with including it in your dues, cool, but in many cases I don't think a nominal fee is outrageous: let the people who want to use it support it, while others who take a break in the winter and will never use the sim not pay for it. (Slippery slope perhaps as you could say that about every amenity at a club.)