Copyright 2012 Robert Clark
Nice video here with Alan Lindenmoyer, NASA's head of the commercial crew program:
America's New Paths in Space.
At about the 6:17 point in the video, Lindenmoyer makes the key point that it's part of NASA's charter to stimulate the commercial space industry in America. Then efforts by some in government to limit NASA's support of the commercial crew program are disregarding a key component of why NASA exists in the first place.
Supporters of commercial space access have long argued that aerospace companies could create a privately developed launcher at costs in the range they spend to produce new jet airliners at a few billion dollars. See this argument for example in Harry G. Stine's Halfway to Anywhere: Achieving America's Destiny In Space.
The problem is there is a much larger market for airline travel than for space travel to pay for those large up front development costs. However, a key result of the success of SpaceX in privately developing a launcher and capsule is that they were able to develop them while cutting 90% off the usual cost estimates for the development of such vehicles. Then following their cost cutting model, instead of the usual estimate of a few billion dollars to develop a launcher it would only cost in the few hundred million dollars range.
This means there is a market that the usual large aerospace companies and even the smaller new ones such as SpaceX, Orbital Sciences, Sierra Nevada, Blue Origin, etc. would have in order to pay back this much reduced initial investment. Such a market is the same as that for jet airliners, private, commercial passengers.
Peter Diamandis makes this point in this effective TED lecture where he refers to this market as "self-loading carbon payloads":
Peter Diamandis: Taking the next giant leap in space.
A well researched example of such a manned vehicle would be the fully orbital, fully reusable DC-Y follow-on to the DC-X. It was estimated to have a $5 billion development cost which would include 4 flight vehicles. However, the important point is as privately developed, that could be reduced to perhaps $500 million to get a fully reusable, manned launcher.