It's a sort of thing that you build when money is meaningless. And at that point you can still have very valid priorities - helping other people out, setting up charities, etc etc. Your house just happens to have a cinema room - it's no different "luxury" than having underfloor heating in your bathroom. It's comparably unnecessary, just on a different financial scale.

> it's no different "luxury" than having underfloor heating in your bathroom. It's comparably unnecessary, just on a different financial scale.

Underfloor heating is not unnecessary, in fact it is about 10% more efficient in operating cost[1] as it can operate at lower inlet temperatures (30-35 °C, compared to 60+ °C for conventional radiators). In addition conventional radiators are often placed on the outside-facing wall below a window, which means that much of the generated heat gets lost.

As for the installation costs, for new construction conventional radiators and underfloor heating are approximately at the same price level.

[1]: https://www.t-online.de/heim-garten/energie/id_73373816/fuss...

And $100k home cinema is more efficient than having to go to actual cinema. Still, a luxury.

No, you want a heating in your home regardless, and if both options have the same cost, then it is not a luxury, it's standard (at least when compared to other modern countries, though)

If you were a billionaire, and 100k was 0.01% of your net worth? If someone owned a €300k home with neither mortgage nor investments, that’s the equivalent of €30.

I’m may not be impressed with their blasé attitude to money, but I bet I looked more wasteful than that to a Nairobi friend of my partner when I visited on a plane ticket that cost half their annual rent, £350.