> It's how we get to the moon and Mars and how we survive as a species. It's what's next.
The core fallacy is to assume whatever made Earth less than ideal will not follow us to the new destination. To assume our survivability as species only depends on the locale, not what we will eventually turn that locale into.
This happened with every new frontier. The romanticism of "it will be better in the new place" is baked into our genes probably because of the explore/exploit mechanism; it is natural for any animal to want to wander off when resource/danger ratio in a place isn't ideal. What we omit is that the most important layer of our habitat is the anthroposphere; us and our artifacts. We will drag the best resources and worst dangers with us anywhere we go.
> that their money is better spent here at home reminds me...
What that money represents is an agreement on commanding other humans' goods and services. As such, how much can that be "theirs" if we are taking a plant scale perspective? Don't get me wrong, I am not trying to inject a purely collectivist perspective here; money works great at certain scales, but for entire-humanity-scale issues it is a rather useless construct to think with.
To me a more accurate perspective is "smart but ultimately single person, thus bounded in their rationality, somewhat exploits the imperfections of our value representation/abstraction layer to redirect tons of goods and services of humanity into what is ultimately a useless vanity gesture that will generate no insight into humanity's perennial problems".