So Everest would be possible? Am I hearing that? No launch costs, you can walk away if you need to (depending on the weather). Has to be cheaper by billions than an orbital station.
It would absolutely be possible to have a base on the peak of Everest. I think you can even get up there with helicopters. The only question is, what would be the scientific value? Astronauts do not go to the ISS just because they love living in cramped quarters for six months... ;)
Live for a year without resupply, generate own heat and power, prove you can survive. And do useful work. Before committing human beings to Mars. The topic of this discussion.