Ok, we need some links with more concrete figures:
Musk figures the colony program — which he wants to be a collaboration between government and private enterprise — would end up costing about $36 billion. He arrived at that number by estimating that a colony that costs 0.25 percent or 0.5 percent of a nation’s gross domestic product (GDP) would be considered acceptable. The United States' GDP in 2010 was $14.5 trillion; 0.25 percent of $14.5 trillion is $36 billion. If all 80,000 colonists paid $500,000 per seat for their Mars trip, $40 billion would be raised.
I'm not saying that's a reasonable way to draw a budget, just to provide an estimate on what Musk is targeting. Since this article came out (Nov 2012), I think his cost estimations went up, and his funding plans shifted more to preparing a realistic IPO (not covering the whole thing, but some of the early stages). Cannot readily find a quote for that.
There are many more (somewhat obfuscated) details in that article, like this one:
Musk also ruled out SpaceX's Dragon capsule, which the company is developing to ferry astronauts to and from low-Earth orbit, as the spacecraft that would land colonists on the Red Planet. When asked by SPACE.com what vehicle would be used, he said, "I think you just land the entire thing."
Asked if the "entire thing" is the huge new reusable rocket — which is rumored to bear the acronymic name MCT, short for Mass Cargo Transport or Mars Colony Transport — Musk said, "Maybe."
“Land on Mars, a round-trip ticket — half a million dollars. It can be done,” he told the BBC.
Musk did hint that one of the keys to low-cost trips to the red planet would be the ability to not only refuel there, but also to reuse the entire spacecraft on the return trip. In the BBC interview Musk said by reusing the spacecraft, you end up with the same sorts of costs airlines face. Musk compared it to flying today where a 747 isn’t simply thrown away after a flight to London. Like the airplane, the cost of the spacecraft could be spread out over numerous flights rather than just a single trip making fuel one of the main expenses rather than the entire ship.
Asked about the possibility of a SpaceX IPO, Musk said the company’s plans are too long-term to attract many hedge fund managers, making an IPO unlikely any time soon.
“Maybe [when] we’re close to developing the Mars vehicle, or ideally we’ve flown it a few times, then I think going public would make more sense,” he said.
So, I can't comment on how realistic is each of his cost and time estimations, but he is trying hard to make them internally consistent, and most and first of all, to bring down the launch costs and to improve the reusability. We can already see several successful steps in that direction, and we will see the gradual progress, or lack thereof, very soon. It's not some Kickstarter scheme for Gates & Buffet.