I think military spending is a fair comparison topic even if not directly addressing your point, it's often argued that it's military/space progress that trickles down into improvements for 'the rest of us', though I have my doubts about that nonetheless it provides an incentive beyond the obvious subject being addressed. I take issue with 'fantasy projects', that's what science is, to distill fact from fantasy, it the fantasy in the first instance that inspires the research that provides the answer, if you're essentially saying that we have gathered enough contrary evidence and should now abandon the search and focus on home, well, I can certainly see that perspective and have felt that way at times, but to argue that because we don't know something, we should not waste money finding out the details, well, I think the Wright brothers efforts would have been dismissed as fantasy at the time, glad it did not dissuade them.