Adam Mann in Wired covers Elon Musk's ideas about putting people on Mars: "Elon Musk Wants to Build 80,000-Person Mars Colony".
That first flight would be expensive and risky but once there are regular Mars flights, you can get the cost down to half a million dollars for someone to move to Mars, Musk told Space.com. Then I think there are enough people who would buy that to have it be a reasonable business case. Musk added that he sees the future 80,000-person colony as a public-private enterprise costing roughly $36 billion.
I'm right now finishing an essay about the constraints on human colonization of space, so to see this topic developing in the news again is a good thing.