An anonymous reader writes with this quote from the BBC:
"Rocket entrepreneur Elon Musk believes he can get the cost of a round trip to Mars down to about half a million dollars. The SpaceX CEO says he has finally worked out how to do it, and told the BBC he would reveal further details later this year or early in 2013. ... 'My vision is for a fully reusable rocket transport system between Earth and Mars that is able to re-fuel on Mars — this is very important — so you don't have to carry the return fuel when you go there,' he said. 'The whole system [must be] reusable — nothing is thrown away. That's very important because then you're just down to the cost of the propellant.' ... He conceded the figure was unlikely to be the opening price — rather, the cost of a ticket on a mature system that had been operating for about a decade. Nonetheless, Musk thought such an offering could be introduced in 10 years at best, and 15 at worst."