There's a lot of different "big science" investments humanity could make. In space alone, there's space stations, moon missions, Mars missions, cheaper Earth-NEO transport, etc., etc.; then there's particle accelerators, telescopes, and every other big science project under the sun (or beyond it).

Two questions: first, in a zero-sum model, why is human exploration of the moon more worthy than other similar unfunded projects? In an non zero-sum model, why is it worthy enough to justify growing the funding pie for science projects?

How many billions of dollars are there in "a little more effort", in your estimation?