I wouldn’t call asteroid mining fictional if focus fusion turns real. The Polywell people are talking $27/kg to orbit, at prices like that asteroid mining and real space colonization become economical. I suspect focus fusion rockets would be even cheaper. One modest nickel-iron asteroid would easily make it worthwhile.
Between asteroid mining, fusion torch recycling, fuel production from CO2, and cheap power making indoor farming economical, I would expect most of the resource extraction we do now to quickly become obsolete. We could have a much lighter footprint on the planet, even as our standard of living improves.
