You maybe forgot what thread you're in. Scroll up to the first comment I replied to to remind yourself of where the goalposts are. In fact in my very first comment I mentioned there "can't be many!," and indeed there are not. We have "maybe platinum if we can just drop it into the atmosphere with no reentry vehicles or if we can autonomously build reentry vehicles using material we find in space."

So far that's the best answer, so thanks for providing it.

You may also find in your scrolling that I did not say "it takes too much energy to ship back." I said "What resources are on asteroids that justify the energy expenditure to get from space and back?"

Obviously getting down is not the expensive part. We've all heard of gravity. Getting the equipment up that is needed to get stuff down is. This is also due to gravity.

I'm afraid you misread my first comment and responded as if I thought it was energy expensive to drop stuff onto earth.