What the hell is a "luxury" gym??
Like anything "luxury". Nicer or perceived to be nicer than average.
Some gyms include amenities or features that aren't found at a bare bones gym, such as membership caps, towel service, specialized equipment, fitness or medical testing, complimentary or innovative group classes (think barre, hot yoga, spin classes, pilates, crossfit), steam or sauna rooms, luxury toiletries, app-based bookings, smoothie bars, clothing boutiques, lounges, spas with physiotherapy and massage, personal training, free childcare, free parking, etc. Honestly, the sky is the limit.
Everybody has their judgement about what is valuable. I wouldn't pay an exorbitant amount of money for a "luxury" gym, but at least it benefits a person's health and isn't as resource-intensive as other "luxury" consumption.
Or maybe you were just making a joke about not going to the gym.