On Tuesday, tech entrepreneur Elon Musk told the world he has a plan to help humanity establish a colony on the planet Mars. But he delivered a sobering fact to the audience at the 67th annual International Astronautical Congress in Mexico: “Right now, you cannot go to Mars for infinite money.”

With the right organisation and traditional methods, he added, you could hypothetically do it for $10 billion per ticket – an absolute best case scenario with current technology. But who wants to pay for that?

Instead, Musk wants his SpaceX firm to develop a new, reusable rocket system that can transport 100 people at a time. That, along with some important technical achievements, would help bring the cost down – ideally to as little as $200,000, or the price of a median home in the United States. Refuelling the ship in orbit around Earth before it heads off to its distant destination would, he explained, be one way of lowering expenses.

Although attractions would make the trip “really fun”, there is a high chance of fatality

Noticeably absent from Musk’s presentation, however, was confirmation that any big backer was ready to stump up the funding to make this dream a reality. Instead, Musk was selling the vision in the hope that a mix of public and private investors would get behind it, he explained.

But he was also happy to admit that there would be human risks involved, too. Although attractions like the on-board restaurant would make the trip “like, really fun”, there is a high chance of fatality. “Are you prepared to die?” asked Musk. “If that’s OK, then you’re a candidate for going.”

Calculating whether plans to colonise Mars are economically feasible is no easy task, but one person who has tried is Sydney Do, a researcher at Massachusetts Institute of Technology. He recently co-authored a detailed review of a different scheme – Mars One – which hopes to establish a Mars colony by 2024. Largely because of the ballooning costs involved in maintaining a human presence on the Red Planet, Do found the plan in its current form “fundamentally unfeasible,” he explains.

“It is expensive in terms of the need to supply them with spare parts, keep systems running that extract water and create gases for them to breathe,” he says.

What did he think of Musk’s project? It’s certainly visionary, says Do, and he noted the huge technological barrier of trying to get 100 people into space at once. The most we’ve ever managed is eight, via the space shuttle. Plus, the spacecraft Musk hopes to fling Mars-ward is very heavy. Do points out that it has roughly the same mass as the International Space Station.

But his key criticism of Musk’s presentation is that it only discussed the relative cost of getting someone to Mars – not the cost of sustaining them.

“A more accurate representation of the problem would be in addition to the cost per trip, how much is the cost per night to stay on Mars?” asks Do.

When asked about colonisation of the planet, and how that would actually work, Musk told an audience member that his company was focused primarily on transportation only. In other words, SpaceX is an airline. They don’t do hotels.

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