It involves launching an untested zero-g mining and manufacturing facilities from Earth. It also needs shielding if we use people there. Mars has gravity and c

It involves launching an untested zero-g mining and manufacturing facilities from Earth. It also needs shielding if we use people there. Mars has gravity and can use our normal mining and manufacturing, it's straightforward to dig in with shovels for shielding. Launching from Mars is easier, so it's a probable path to the belt. I don't see economical viability for the Earth in any of these scenarios. Maybe only the straight breakthrough in zero-g autonomous mining and return of precious metals from the belt to Earth.