New York (CNN Business) A space revolution is upon us — so says the new wave of tech entrepreneurs pledging to colonize the cosmos.

Several billionaires and their hard-charging rocket companies say the tiny roster of humans — 573, by the count of space expert Jonathan McDowell — who have flown to space is about to get much longer. They promise that more Average Joes can have experiences long relegated to highly trained astronauts.

But the galactically curious should take heed: Space travel will probably remain prohibitively expensive for anyone outside the 1% for a long, long time.

A stay on the International Space Station costs tens of millions of dollars. A group called Space Adventures has offered wealthy individuals the opportunity to fly to the station aboard Russian-built rockets, and so far seven clients have made the trek. Most recently, Cirque Du Soleil billionaire Guy Laliberte paid $35 million to spend a couple weeks in space. And after NASA announced earlier this year it would open the US portion of the ISS to private astronauts, Bigelow Aerospace said it would coordinate rides for $52 million a seat.

SpaceX is also planning to charge an undisclosed amount of money to a Japanese billionaire for a moon mission slated for next decade.

On the cheapest end of the spectrum is Virgin Galactic. The company set up by Richard Branson plans to offer 90-minute flights into the upper atmosphere for about $200,000 to $250,000 each. That's roughly the median home price in the United States.

Virgin customers will board a six-seater space plane, called SpaceShipTwo, that will climb to 40,000 feet nestled beneath the wing of a mothership. The rocket-powered plane will then detach and fire up its engine while passengers white-knuckle their way up to 50 miles above ground , a boundary considered by the US government to mark the beginning of outer space.

Galactic acknowledges that its current clientele is upper crust: Most of the 600 people who have signed up for rides have net worths topping $10 million, according to recent disclosure documents. A third are worth $20 million or more.

Branson, for his part, has pledged to start lowering ticket prices after Galactic recoups some of its steep R&D costs, although he wouldn't say how low they could go when asked by CNN Business last year.

Some analysts are confident space tourism flights will become less expensive. The price of most technologies, from commercial aircraft to television sets, drastically declines over time.

"The price point is high, but that's just like any other early adopter," Ann Kim, managing director of frontier tech at Silicon Valley Bank. "It will come down."

But by Virgin Galactic's own metrics, people are willing to spend up to 1.5% of their net worth on a single discretionary expense. That means, even if Virgin Galactic manages to cut ticket prices by 90%, its target customer would still need to be worth $1 million to $2 million.

The far-out future

Space vacations may remain out-of-reach for most of us in the foreseeable future, but many space enthusiasts insist that one day humans will be zipping around the solar system to work on other planets or orbiting habitats.

Today, the most well-known space visionaries are three billionaires: Branson, SpaceX CEO Elon Musk and Blue Origin/Amazon founder Jeff Bezos. They've gained die-hard fans, as well as critics who question how equitable the future of space travel would be if it is built by the world's most affluent people.