These are the types of projects where a single billionaires great wealth can inspire other investors to come along. If Musk couldn't pour millions into his ventures, it's unlikely the average investor would have followed him into space.
In addition, the USA invested in the internet, space and atomic weapons solely for the purpose of war, even the hubble is based on military technologies. I am again concerned that people are arguing for a future that's dependent on the needs of politicians or the military.
Even China was smart enough to see value in the capitalism model. Allow for the ability of great wealth, allow the private citizen to decide how to deploy the fruits of their work and something good might come out it.
Also, the Government has taken over a billion dollars in tax from Mark Zuckerberg, so the Government has plenty to play with. Remember, it's always easier to play with other people's money, hence the inefficiency regarding the use of tax dollars.