Unfortunately, space programs tend not to produce revenue for a long time. Perhaps the technologies developed could be patented, and the revenue from that shared between stockholders, although, then the stockholders would probably focus on just developing the tech, as opposed to actually doing anything.
It is rather hard to disagree, however, that NASA could do more with its 17 billion dollars. Some fusion of government and private technologies would seem to be expedient, although I'm not sure exactly what that would be.