Every year, the US government grants NASA a budget of tens of billions to fund its terrestrial and extraterrestrial research. Just last month, President Trump signed an order confirming it would get $19.1 billion in 2018 in what he called a "national commitment" to "human space exploration."
Space is expensive, and it's the main reason why the agency has stepped back from its own rocket launches. However, a number of private companies have stepped up in its place, all of which are financed, in part, by billionaire businessmen. Amazon founder and CEO Jeff Bezos, for example, has revealed that he is selling about $1 billion in Amazon stock each year just to fund his personal race to space.