> I would bet the US DOT, for example, is as costly or more in terms of monetary input->realized output of all the federally supported space agencies.
No. Everyone uses and needs roads and other kinds of transportation. No one actually needs space probe pictures or chemical analyses of Mars rocks, so that output should arguably be valued at 0 when you're evaluating "monetary input->realized output." NASA could be incredibly "efficient" at turning tax dollars into large volumes of esoteric research findings, but that money would still be better spend on less efficient organizations whose output is far more valuable (e.g. giving large numbers of real people access to medical care).
This might make my point clearer: think of NASA as an organization that builds giant stone penises in the desert. NASA is very good at that job, efficiently builds a lot of them, and I suppose the penises provide some shade. But do we really need them (even if some people are huge fans and are really inspired by them), when that money could be used to feed people who have no food?
> Regularly, highway projects in any of the 50 states turns from "3 months, 30 million" to "actually, 2 years, 110 million." and VERY rarely is that challenged by the public. It is mind boggling, as it's our tax dollars going to the pockets of scummy contractors connected to politicans.
That's a problem, but it doesn't have anything to do with the question of what output to prioritize.
Now don't get me wrong. NASA does do some valuable stuff, but that stuff doesn't have anything to do with Mars or taking pictures of deep space.