I bet the value of metals on Earth already far exceeds this many times over. And what do you think would happen to the price of metals if you had this huge supply?
You could make exactly the same argument, with the "action" as keeping funding NASA. We need to establish that giving ANOTHER $18 billion is a good use of funds compared to leaving it in the taxpayers' pocket. Any economist will tell you that $18 billion in tax revenue actually costs the economy more than that (for example from deadweight losses).
This argument is often trotted out, but it doesn't hold water if you think about it. There may be some examples where the technology has been re-used, but what's their value in terms of useful research quantitatively, rather than hand-wavingly?
Even if it's as high as 20% that can be re-used, you could get 100% of that value by researching image-sharpening, disaster shelters, food storage, wireless comms and all the other things you mention, directly. So you still have to justify the remaining 80% in other ways, the side-effects already accounted-for.