Elon Musk incidated in a speech that humanity should be willing to spend about one quarter of one percent of GDP for Mars colonization civilization insurance, and Musk said a ticket price of about $500,000 per per person would likely be affordable for about one person in a million. Since humanity will tip the scales at 8 billion by the time the architecture for living on Mars would be available, 8,000 people could afford to head out to Mars.
Mars is the closest potentially habitable planet, he’d like to send people there. He’s not talking about establishing a small base, but sending large numbers of people to live there permanently. He sees this as “life insurance” for humanity in case something happens to our planet, be it a natural catastrophe or a human-caused event.