One of the most exciting aspects of the renewed interest in space these days is that we have once again the chance of start building things in space quite soon (unless the world economy collapses 100% finally and war is waged). Once we can get to space cheaply people will start experimenting with all forms of propulsion up there because fuck-the-government and that is not easy to do on Earth or even just launch from down here.
Which is why, space mining will likely never benefit Earth. Any material 'up there' is so much more valuable in space than dropping it down to Earth to make Coke cans or whatever.
There are designs to couple the dropping of one thing to the lifting of another, like an elevator (though not necessarily at the same time). This makes delivering payloads to Earth necessary for your launch system. They might as well be valuable payloads.
Yes I can imagine Earth financial markets will speculate in space-based industry. Grounders may become 'wealthy' from off-world activities, but without ever actually benefitting from them directly.
I imagine the amount of stuff floating around up there is so vast, once you can build all the heavy, bulky parts of a propulsion system in space, produce fuel in space, and automate the mining, you could truck absurd amounts of all kinds of raw materials to Earth, easily more than you could realistically use in orbit short-term. But I guess people could be made to pay a pretty penny for Space Gold accessories – or space diamond, space platin, space whatever. Say, an Apple Watch milled from a solid chunk of Space Platin or even Space Diamond, I think that might sell pretty well.
As to getting the stuff down, I imagine one could do that relatively low-tech; cut it into manageable chunks, wrap those in some kind of simple heat shielding, deorbit to some remote place and have some kind of parachute system slow it down enough to not disintegrate on impact; a chunk of solid gold should be able to take quite a beating.
Have it mined optically in space and then molded/vacuum deposited/3-d printed up there into (passive) lifting bodies of appropriate proportions out of comb like structures, put a jetpack for steering onto it which brings it down into the atmosphere in a controlled way, detach that (reusable) jetpack before burning up, reroute to some orbiting space dock for refueling.
Meanwhile, have a massive golden glider splashing down into the ocean somewhere near a cost, and have it towed by tug-boats towards the smelters, forges, metal works, catalyst producers, whatever...
