>If it's constantly being used, it will wear out faster.
Yeah, but there's an absolute limit to that, beyond which the cost doesn't keep increasing. Beyond that point, the QoS goes down (queues).
>You are conflating "we price based on expected under-utilization" with "costs don't scale with usage."
I'm not conflating anything, I'm responding to what you said:
>If gyms faced a situation where people would go and spend 18 hours working out every day for a month, they would probably change how they billed things.
Why would a gym need to change how they bill things if all their customers were aiming for maximal utilization, when their costs would barely see any change? I doubt your typical gym operates on razor-thin margins.