>Following the example of colonial America, let’s pick as the affordability criterion the property liquidation of a middle-class household, or seven years’ pay for a working man (say about $300,000 in today’s equivalent terms), a criterion with which Musk roughly concurs. Most middle-class householders would prefer to get to Mars in six months at the cost equivalent to one house instead of getting to Mars in four months at a cost equivalent to three houses.
Colonization of America was extractive. You send colonists and they survive on their own and even pay taxes and you get products back. That's not what would happen on Mars. There is nothing so valuable that it would be worth carrying back to Earth. At the same time it would take huge amount of money to support high-tech colony in Mars until it can support itself.
I imagine that the cost of moving people would be insignificant compared to the "colonization kit" that would enable the colony to become self sufficient. Developing that kit would probably cost more than all technology needed to move people to Mars. Just imagine the amount of technology transfer needed to build and maintain maintain systems for breathable air (air tanks, seals, valves, inspection equipment, instrumentation, automation electronics) without help from the Earth. Until Mars settlers can build things in-house, they need constant economic support from the earth.
ps. We don't even know how to sustain biosphere in closed environment yet.