Mars is a nightmare, but the richest and most important people alive (Musk has more votes than the others
https://bitcointalksearch.org/topic/most-important-person-alive-5353987) wants to create a colony there.
He is going to evaporate half of his fortune, but he is obsessed and he'll manage to create a small colony on Mars.
Forget about the million or even 5000 thousand people there, until the voyage takes less than 3 months and the radiation and low gravity is solved.
Some States will pay him billions to keep some military personnel there for political reasons.
But I can't see that having any economic sense until some resource is found on Mars.
I think he said he would evaporate most of his fortune to get human beings to be a multiplanetary species if he has to. I think once you have more than 5 billion dollars, money probably stops mattering to you for your own personal wealth.
I'm not sure they've solved the radiation issues with Mars either. That's why Elon Musk started the Boring company. I imagine that at least during my lifetime, the best we can hope for is people living in deep caves beneath Mars' surface.
As for economic reasons... If they spot an asteroid "planet killer" heading on a direct course to Earth, Elon would be able to charge literally anything he wanted to get people to Mars. Even if there's a legitimate scare, he'd be getting billion dollar offers for a seat. So I try not to think he's too crazy. He could end up saving mankind. Also of note, at the rate we're burning fossil fuels, the window of opportunity for mankind to become a multiplanetary species is quickly closing (at least until we start throwing rockets into space with electric powered catapults, which is what I think will eventually happen for satellites and other unmanned craft).