Can private-sector space business be profitable, or is it just an exciting way for billionaires to live out their fantasies?

Mars One, the non-profit group planning a one-way trip to the red planet in 2025, got lots of media attention this week when it announced it had narrowed its pool of potential astronauts to 100 candidates from around the world.

But there are 6 billion reasons to believe they won’t make it.

I refer, of course, to the $6 billion budget Mars One says will be required to lay the ground work for and launch its first manned mission. We’ll assume that $6 billion is enough money to meet its goals, although space projects are notorious for cost overruns and delays. Even then, it’s not clear that Mars One will be able to collect close to that amount and meet the mission goals. “We do not disclose these numbers at this time,” Bas Lansdorp, the CEO of Mars One, said in an e-mail.

Start with what’s expected in the near term: Per Mars One’s timeline, it plans to open a simulation colony here on Earth this year, so their astronauts can begin training for the mission. While the organization announced plans to start building, it has yet to reveal the location or any further details on construction. “We’re still on track to have that ready after the summer,” is all Lansdorp would say.

Mars One’s next goal is in 2018, to launch a communications satellite to orbit Mars, and a robotic lander to demonstrate the viability of various technologies needed for the manned mission. In 2013, Mars One announced that Lockheed Martin would build the rover, and that Surrey Satellite Technology Limited (SSTL) would build the satellite.

However, Lockheed Martin told Quartz that, after it completed a concept study on how to build a lander—based on one it had previously created for NASA—Mars One has yet to issue further instructions. “We’ve concluded the study and are waiting to hear back on the next phase for them,” Gary Napier, a Lockheed spokesperson, said. And today, Space News reports that SSTL also has not heard back from Mars One after completing a study on the satellite.

“Mars One is studying the results of the work done by our suppliers to date,” Lansdorp writes. “Our first unmanned mission has our highest priority and we expect to award follow-up contracts soon.”

Yes, 2018 is still three years away, but the timeline for the development, construction, testing and launch of a mission to Mars—even a robotic one—is quite tight, and would need to commence almost immediately. Plus, rocket launches are typically scheduled, and paid for, years in advance.

Will Mars One have enough cash on hand to meet these demands? A mission like the one it describes will cost several hundred million dollars—the Phoenix mission that Mars One is basing its lander on cost $386 million, including launch, and didn’t include a satellite as well.

Mars One says it plans to finance the mission through sales of branded items, donations, sponsorships and, most importantly, a television deal to broadcast the voyage and activities of its putative colonists. It uses the Olympic games, which earned $8 billion in the 2009-2012 period, as a benchmark for potential earnings. But the difference in entertainment value between the Olympics, a time-tested global audience draw, and a mission to Mars that will start with several months of boredom, suggests that Mars One’s hopes are overblown.

Certainly, it appears that no media outlet purchased the exclusive rights to broadcast Mars One candidate interviews.

Indeed, the organization was unable to raise its full $400,000 goal in an Indiegogo fundraising campaign, launched last year to boost the lander mission. Global foundations with billions of dollars are largely funded by the largesse of a billionaire or major corporation, but most billionaires interested in space exploration have been founding their own companies to do so, not giving their cash to Mars One. Even a successful space start-up like SpaceX, which shares Mars One’s goal of reaching Mars, has only raised $1.2 billion in funding, and has likely not come close to earning $6 billion.

Without more transparency from Mars One about its financial plans—or a sudden windfall of cash—it’s hard to see how it could possibly succeed in launching a robotic mission to Mars by 2018, much less send people there by 2025. Its boosters have argued that this is a chicken-or-egg problem, and that building excitement for a Martian mission will help generate the cash to see it through. But building that excitement without the realistic possibility of a pay-off could also let down millions of space fans around the world.

This story was updated 2/20/15 after Mars One responded to our request for comment.