"Nobody these days surprised that producing stuff in China and delivering it 10000km is cheaper than producing locally"

Actually people do see the madness in this, hence all the "produce local" initiatives instead.

The only reason it made sense, was not caring about external costs from fossil fuels and bad worker conditions in china.

"You could use the energy needed for a rocket start to melt and seperate it from allmost any rock here on earth way easier.

good luck getting permit :)"

Not hard. What do you think recycling smelters do?

It just does not make economical sense to melt and separate any rock and purify the elements. You use the ones you know have already high amounts of iron, copper, .. and you seperate them before as much as possible as smelting is energy intense and handling molten elements is hard and therefore expensive.

And the other point, yes, if there is a automated space industry, that can produce cheap reentry vehicles, some space mining might make sense. But if we would have that tech, we might as well use it on earth. Because you cannot just point a lump of iron towards earth. That would be called a asteroid and would be a weapon of mass destruction. You need spaceships. Going down .. and then up again, unless you use throwable spaceships?