The future economy in space is so much larger than the future economy on Earth, that it doesn't make much sense to ship non-rare materials back to the surface.

The future economy in space is so much larger than the future economy on Earth, that it doesn't make much sense to ship non-rare materials back to the surface. There are some where I think it will, for the foreseeable future, just because they're so rare in the Earth's crust and so plentiful in asteroids, but long-term, microgravity assembly plants are how things will go.