On shipping material mined from asteroids to Earth, umm...actually, my thinking is that robotic unmanned barges could be run very cheaply. I mean if you are just talking about shipping a large quantity of precious metal to Earth, then you only have to worry about lift-off and getting it on just the right vector so that it eventually makes a reasonably slow approach to Earth or its moon. You do not have to constantly propel the shipment all the way through the solar system. Once you had established an economy of scale, the shipping cost would end up being rather cheap, maybe even cheaper than shipping by sea. We are talking about a relatively frictionless environment.
The problem is getting it down to the surface in a usable and accessible condition, without harming the environment or the local population.
Meteors bring between 40 and 80 thousand tonnes of material to Earth each year right now; But it mostly arrives as dust, which is useless, and what arrives in larger pieces either turns to dust on re-entry, rendering it useless, or stays in one lump, rendering it highly dangerous.
Getting stuff down in remote areas is probably fairly easy to arrange, though it requires very precise control both to prevent loss (to burnup or to deflection off the atmosphere), but ore in remote areas we already have lots of, without the hassle of going to space for it.
What we really need is a space elevator.