How gyms stay in business

    Anyone who has tried to buy their own gym equipment knows how expensive it is upfront and the maintenance is also quite costly, so looking at large gyms that have dozens of these machines it is hard to imagine how they stay in business. The success of gyms mostly has to do with the large market they serve and how little the consumers actually use the product they buy. In fact, only eighteen percent of gym membership holders use the gym regularly.
     The other eighty-two percent of gym membership holders mostly subscribe as a result of New Year's Resolutions and the appeal of the idea of going to the gym. This means that they will sign up for plans and then the gym will use an automatic billing system to continue collecting money from the members without them remembering to unsubscribe.

                                                      
      Gyms know about this habit of people to sign up and forget about memberships so they will often allow many more people to sign up for memberships than the gym has capacity for. For example, most Planet Fitness gyms can only hold about three hundred people at a time but they each have around six thousand five hundred members. These extra members are pure profit for the company because they don't contribute to the wear and tear of the equipment and they don't use the other amenities like showers that the gym provides. So, despite the high upfront costs of owning a gym, the human behavior of most gym customers is what allows them to stay in business and turn such a large profit.

Sources
https://www.fool.com/investing/general/2015/05/23/exorcise-your-ghosts-of-spending-past.aspx