Underground listening room?

I have about 6 years of learning about my underground listening room, pros and cons. I learned the hard way about the leak factor, french drains, killing trees, spending thousands of dollars. I know now what works and what dosent.

I live in the middle of no where. My room is open on one side, the side that is exposed to the hill it is built in and has outside stairs and outside entrance. I love it. I can close up the room and go to a concert, or open up the doors and go outside and have an amiptheater. When it is closed there is hardly any noise to the outside world, its got to be the underground sound asorbtion thing.

But what about you rich city people. Is this something that would sell. I think I have figured out how to build on or around site, and install an underground room, and according to the elaborance of the entrance ( elevator to stairs) would directly affect cost but if you could step outside, go down a few stairs behind the house or shop and go to a 20x20 or a little bigger hide away, get away from the world and watch movies, rock out, classical the day away, or hide from the wife and kids ( or storm shelter )
where I live.

Its not for everyone, could cost some dineros.

I like the m&k pro setup for something like this but you could put any setup and the room acoustics would be designed before install to get sound reflection right.

Movies, Big Games 100" + , Kid (teen) room, Big Boys room?

Can be decorated to any taste, fine, abstract,modern,east indian,baptist church?

What are your thoughts?

Kelton