I'd agree about the economics; when Musk suggests people getting out a loan to make the trip, what bank would grant that loan? How would they collect on it? What's Mars going to sell to Earth, which it needs to in order for a bank on Earth to accept a repayment? When he says "People will want to create the first pizza joint [on Mars], the first iron ore factory", that makes me cringe — the former because it's the kind of low-income role that needs food stamps in California (or at least, I know someone, n=1, where that was the case) and can't possibly afford that trip even with his price optimism, and the latter because if that's not already fully automated before you arrive, you probably can't build the colony in the first place.

I do however expect that there's enough psychological draw from "the final frontier" to get a million people spending $100k USD for the trip. Can he get that cheap? No idea.

> I don’t see the analogy here at all. Yes Columbus took a risk, he did that because he and his investor expected to make a lot of money just like the Portuguese going around Africa did. How is that relevant?

Because what he was actually aiming for wasn't possible, he just got lucky there was a (just about possible) alternative that he happened to find purely by coincidence.

What I'm expecting, is that we get von Neumann replicators before a Mars colony reaches the current population of Greenland (56k), let alone a million, and also that a lot of people will prefer the Moon instead (the ways in which the Moon is harder are not ones I expect to be important compared to the difficulty of either). But I also expect that some random thing which gets invented specifically as a result of the attempt to colonise Mars to prove really useful in some impossible to predict way.