If memory serves, during the height of the Apollo program, some 300,000 Americans were employed to make it happen. Only a small percentage of that amount worked for NASA. The rest worked for companies as big as Grumman and North American Rockwell down to small outfits like the bunch of elderly women who hand filled the CM's heat shield homecomb structure (as mentioned by Tom Hanks in the "From the Earth to the Moon" series).

In truth, NASA actually builds very little on its own. Instead, it contracts the work out to thousands of contractors at companies big and small. NASA didn't launch the MERs to Mars, Boeing did (with help from the Air Force).

If people hope for the private sector to pony up billions to build their own spacecraft in the hopes of striking it rich in space, well, that's very unlikely to happen. To date, about the only space ventures that have really made much money are satellite communications and perhaps Earth resources imaging. Even if the moon were covered in gold dust, it wouldn't be worth the expense to go there.

Corporations are in business to make a profit, imagine that. They also expect a return on their investment in line with the associated risks. That's why the notion that corporations would invest billions in the hope of winning some prize (but only if they succeed) strikes me as being completely disconnected from reality.