What if you could send a swarm of small "thruster bots" out to attach to an asteroid and push it into an Earth/Moon L point for harvesting and that you could do this for just a few million dollars? At a return of investment 1:1000.
Because the technology to get in space is exactly the same as it was in 1967 - primarily liquid fuel rockets with the occasional use of solid fuel boosters. Strictly Newton conservation of momentum is the only thing that gets you off the planet. Gravitational assist PLUS NEWTON is what gets you further out than Mars. Cassini a ONE WAY Saturn probe cost $5,000,000,000 in today's dollars You come up with a quantitative measure of how much it will cost - not some BS you concoct out of air and wishfull thinking. and remember you will need to get sufficient propellant to brake at the asteroid and to break out of solar orbit and return to earth.
The problem with space enthusiasts is that they NEVER figure out how much something will cost - THey read too much science fiction and confuse it with facts