[DennisP]

NASA's big project for launch is a disposable rocket using Space Shuttle technology. It will cost at least a billion dollars per launch.

SpaceX's project is a fully reusable rocket, with rapid turnaround because it uses methane fuel in the world's first clean-burning full-flow engine. They expect to be able to launch three times per day. On top of that the rocket is built of cheap stainless steel instead of carbon fiber.

With that amount of reuse, each launch basically pays for fuel and ground support, each of which costs about a million dollars per launch. Given their payload of at least 100 tonnes, that's $20/kg. They've already done a single-engine hop test, and hope to reach orbit within six months.

Here's a great video on what makes the new SpaceX engine revolutionary: https://www.youtube.com/watch?v=LbH1ZDImaI8