This borders upon one of my favorite topics actually - there ARE resources up there, which WOULD be valuable, but the cost of getting machinery and equipment up there is literally astronomical. Little known in public circles is the additional (and also enormous) cost of getting shit back down safely.

In order to be cost effective, the stuff we put into space would need to stay there. Asteroid mining is only better than break-even in terms of resources if it DOESN'T come back to earth! For instance, if we had an orbital (or lunar) habitat for refining and manufacturing, where an asteroid capture and retrieval vehicle can be built, fueled, and launched, and then return to, ONLY THEN would it bring back more useful minerals, chemical compounds, and other materials than it would take to launch...

... because the simple fact is that it takes a shit ton of energy to leave Earth's gravity well and destroys a lot of resources in terms of making (and surviving) that journey.

And then instead of building stuff on earth that consume an order of magnitude more than their construction in just transit, we can build it ALREADY UP THERE. That brings us to the last problem, though:

It's no use to any person except someone who is already up there, too.

I'm not even talking about money cost here. Money has no point here until there are humans who want things and need a means by which to measure those wants against the context of what productive capacity is available, represent the magnitude of their want, and represent the transfer of material goods to satisfy those wants. AKA respectively a store of value, unit of account, and medium exchange--the definition of currency.

Space will only be profitable in space.