It’s OK to have your eggs in one basket as long as you control what happens to that basket

There needs to be an intersection of the set of people who wish to go, and the set of people who can afford to go...and that intersection of sets has to be enough to establish a self-sustaining civilisation. My rough guess is that for a half-million dollars, there are enough people that could afford to go and would want to go. But it's not going to be a vacation jaunt. It’s going to be saving up all your money and selling all your stuff, like when people moved to the early American colonies...even at a million people you're assuming an incredible amount of productivity per person, because you would need to recreate the entire industrial base on Mars. You would need to mine and refine all of these different materials, in a much more difficult environment than Earth. There would be no trees growing. There would be no oxygen or nitrogen that are just there. No oil.Excluding organic growth, if you could take 100 people at a time, you would need 10,000 trips to get to a million people. But you would also need a lot of cargo to support those people. In fact, your cargo to person ratio is going to be quite high. It would probably be 10 cargo trips for every human trip, so more like 100,000 trips. And we're talking 100,000 trips of a giant spaceship...If we can establish a Mars colony, we can almost certainly colonise the whole Solar System, because we'll have created a strong economic forcing function for the improvement of space travel. We'll go to the moons of Jupiter, at least some of the outer ones for sure, and probably Titan on Saturn, and the asteroids. Once we have that forcing function, and an Earth-to-Mars economy, we'll cover the whole Solar System. But the key is that we have to make the Mars thing work. If we're going to have any chance of sending stuff to other star systems, we need to be laser-focused on becoming a multi-planet civilisation. That's the next step