This is why the idea of asteroid mining is so abjectly silly. There’s no dilithium or Naquita or unobtanium you can only get from asteroids that you can’t get from earth, and as incredibly expensive as ocean floor mining may be, it’s trivial compared to asteroid mining.
Unless the Mineral rights are controlled by the UN. Then Asteroid mining might start to make sense.
Some of the nickel-iron asteroids can almost be smelted to stainless steel because the purity is so high.
The best thing about asteroids is that nobody owns them. Its the New World without the pesky natives.
The problems Earth-side are political. Unstable governments, corrupt UN, environazis, etc.