If a server costs X and the amount of free users is Y and VIP is Z then you’d need to create an equilibrium where you can make more money to sustain the infrastructure and have enough in case it goes belly up.
Aka: If 10k users are free, and the income from VIP or ads is Z then you have to limit the capabilities of the free users to sustain the platform which in turn can stay (to some anount) free because the VIPs pay for it.
Means: Limit API calls.