SpaceX launch costs are 3 to 6 times lower than that of comparable NASA invented rockets.
It will be interesting to look back on this twenty years from now and see what it really costs to launch a man on a commercial launcher. I suspect it will be nowhere near 3 to 6 times lower.
Although not commercial, but Soyuz already costs about 20 times
less per launch than the Space Shuttle does. And Soyuz is manned
ESA bought Soyuz and will launch it from French Guyana (unmanned). But still: it's not even commercial.
Regarding SpaceX and so going commercial:
The Falcon 1e launch already costs only about 10 million dollars for a 1 ton payload to low earth orbit.
For the money you need to launch one Space Shuttle mission to the ISS, Falcon 9 will launch
12 times to the ISS. The development cost of Falcon 9 is only about 380 million dollars. And the vehicle already is almost prepared to lift of in March/April. Compared to that: the Ares 1 development cost would be at least 40
billion dollars until 2015, to a status Falcon 9 already has reached now by just a few hundred million dollars. The Ares 1 development for now already has swallowed amazingly 9 billion dollars, which is over 20 times more than the Falcon 9 development did cost, whilst there isn't even any Ares 1 launch vehicle. All that exists is a first stage booster, and a Ares 1-X dummy rocket that consisted of nothing more than just a 4-segment STS SRB with mockups on top of it. No second stage engine, and no second stage at all. Nothing. Not even Orion came close to the current status of Dragon.
Falcon 9 has successfully passed both, first stage and second stage full duration tests on ground and is almost ready to lift off. An Ares 1 vehicle did never exist until today but the development has already swallowed 9 billions dollars. No estimations but just current numbers: Falcon 9 already is way more cheaper than the Ares 1. That's exactly why NASA has made a contract and will have to support such commercial stuff in future. There are about 800 people working for SpaceX, which have boosted a privately deleloped rocket into space, versus NASA and its highly costly infrastructure and thousands of employees that did launch a true to scale model rocket only one time based on more than 30 year old hardware, that already costed more than the entire Falcon 9 development