My take on the Spacex is Mars habitation project is that Musk will put a bunch of edgelords on Mars, and then not really be able to follow up with adequate supply lines and the operation will be offline for a hundred years or so while the climate settles down. The people who live on Mars will then have been there alone for a century and in the 2100s we will send a follow up mission with hilarious consequences.
BTW you can tell I'm not Thunderf00t because he says that "the taxpayer" paid $3 billion. I would never use "taxpayer funding" language, I would only ever call it public money (because Treasury creates money when it spends).
The most succinct way that I have found to express the relationship between taxation and spending is that spending at the federal level is constrained by aggregate spending this year, not tax receipts last year.
the government can also destroy money about as easily as it creates it, too. it isn't a politically (and usually economically) desirable thing to do. when it's done, it's usually via replacing the whole currency wholesale (e.g. brazilian real).