There is value in an audacious mission. Even when the end-goal is not directly capitalizable. The tech required to master Mars is so badass that upon development it turns out to be remarkably valuable on Earth, not least because no other team has the determination to follow that hardest path. I suspect that the option value of a Mars colony, fully considered, could be capitalized over an appropriate timescale. But the tech required to just barely make Mars viable is so massively performant on Earth, that it opens up all sorts of terrestrial option value that we otherwise might never have explored.