Elon actually had to state this point explicitly on the livestream because it seems to be not getting to people - SpaceX is not in business of colonizing Mars, it's in business of getting colonizers to Mars (and back). I.e. transportation infrastructure. Elon leaves setting up a colony to other people. That's why he keeps repeating that the idea is to drop the price per person to ~$200k - he seems to believe that if he can pull this off, the rest will be done by others.