I'm a huge fan of SpaceX, and think they (and other like them) represent the future, but they have a little ways to go before they are completely financing their own R&D (at the moment they're still spending a lot of public dollars).
SpaceX arguably wouldn't be here today without NASA's cash.
https://arstechnica.com/science/2016/04/without-nasa-there-w...
Looks like both NASA and SpaceX got a good deal.
NASA today exists, in part, to do exactly that, and has benefitted tremendously from their SpaceX partnership.
http://www.spacex.com/missions
About half the missions on there are non-US government flights.
The private sector would have no incentive and little ability to mount these missions.