I find it nice when persons have dreams.
Only as long as they stay dreams, only.
History is full of dreams. Some even had fanatic followers.
Dreams come from drug abusage, mental desease or at best are just mental garbage disposal.
They can give clues about a persons mental state, but better be not confused with ideas.
Every creative one knows, you need to have one hundred ideas to get a good one. And that one needs to be tested if it's actually feasible
and useful. And any good, feasible idea needs a hundred good ones more to be realized.
A dream is nothing but a vague cloud caused by untested ideas going beserk uncontrolled. Or short: BS
Imagine a city on Mars:
You are aware of Mars is uncapable to hold an atmosphere, are you? And even if it could, how your're going to provide one? Flying billions of gas bottles to Mars, sucking air from our own atmosphere? BS.
If there only can be some kind of a space station. Do you have any idea how the environment of the ISS is like?
Besides it's pretty cramped it's very noisy and loud, because of all the fans and pumps of the life system. It's more kind of being in a submerged submarine than sitting on your sundeck with margaritas watching the ocean.
Who's gonna to live there? Elon? For sure not.
And what the people shall living there are going to do there? Vacation?
If at all this could only be some some kind of a sweatshop where low payed humans are outsourced - banned - from Earth, living in something like an egg farm. But you better build such a thing in Earth's orbit, not on Mars, to keep the ways of the supply chain short.
Do you want this? Think carefully. It could be you or your kids being banned there.
Of course people like Elon want that: Even more people working at even lower wages, at best all for none wages at all. That's why to me all such ideas smell of trying to subtle introduce slavery again.
Instead of asking the question: How much money can a single human spend in a life time?
That's a nice funny thought experiment you may can do when you have a hour or two:
Get yourself a bottle of beer, or whatever you enjoy, start an empty spread sheet, and then imagine you won the "hyper lottery" as much money, as you want imagine - 400 millions, some billions, what you like, doesn't matter.
Then into the spread sheet you entry all what you can imagine what you wanna buy: a Ferrari - make it three! A real estate with 4k m^2 space and two thousand acres land. Larger? Enter it! One in France, one in Canada, one on some tropical island, which you also buy? Enter it! A yacht? Make it four!
Then you add the numbers, what you estimate (or even know) what all that would cost.
Add the sum!
In most cases you will not even reach a single billion. You will spend hundreds of millions, but not a billion.
And then ask yourself the question: What are you going to do with all that stuff?
The true answer is: Nothing. Because you have no need for all of that at all. You only can drive one Ferrari and live in one house at a time. You may have one resident and a vacation place for summer and one for winter. After a few years you will stay in one place, only, unless there is a real reason you have to go somewhere else. You don't fancy to move between all your places all the time anymore. And you will drive some common car, just because it's way more practical. All the rest is unused, just stored somewhere, only dusting and costing maintaining.
And worst part is: You're being very unhappy. Because all what you deep down actually really want, is sharing some beers with friends, playing PlayStation and have some good laughs. But you don't have no friends anymore. Only servants and arse-lickers around you.
That's exactly the problem with people like Elon:
It's not about becoming rich anymore. How more richer can one become?
They are so cocksure they are convinced rock solid by themselves every of their own mental short-circuits is an useful idea. And when they have a lot of money, they not only can pick from enough arse-lickers so eventually there is no one left to contradict, to put some perspective into it, but alas they also have the capability trying to realize their madness.
And that's exactly why there is democracy:
Because single person's dreams are always doom.
Especially when they took off and lost ground catastrophy is unpreventable.