As much as I'm a fan of space exploration, it's a bit silly to say that an asteroid is worth $20 trillion.
The ore in an asteroid, REFINED, is worth that much.
It's a fair bit of work to move that ore from pt A to pt B, crush it, smelt it, refine it, anneal it, etc.
A cubic kilometer of sea water is worth a similarly preposterous amount ... and yet, noone has become a trillionaire by refining sea water. It costs more to do it than the minerals are worth.
Will it happen some day? Sure. Is it relevant today? No.
The ore in an asteroid, REFINED, is worth that much.
It's a fair bit of work to move that ore from pt A to pt B, crush it, smelt it, refine it, anneal it, etc.
A cubic kilometer of sea water is worth a similarly preposterous amount ... and yet, noone has become a trillionaire by refining sea water. It costs more to do it than the minerals are worth.
Will it happen some day? Sure. Is it relevant today? No.