When you pay the subscription to the gym, you actually don't go because you have no incentives. It is a fallacy to think that: "Because I pay, I will feel compelled to go". However, there is another possibility:
Imagine you pay 50 per month to go to the gym, and you get 5 back every time you join a class. You would be actually receiving money from the gym, and thus it would be an incentive to go. From the gym perspective, if you show up 8 times a month, they are still making 30, perhaps what they are already charging.
Could this approach also work if you would use it as money incentives to build a community?