There are a lot of elements that are rare in Earth's crust because during its formation, they settled into the core, and only come out in volcanic eruptions. I've heard that the Earth has something like 20 billions times as much gold as has ever been mined.
Asteroids do not have this problem. (That's how they could pick out that the asteroid killed the dinosaurs, from the odd composition of the layer of mud at their deaths.) Of course you have to deal with space and finding the asteroids and identifying the right ones and mining, but -- supers!
One wonders what amazing things they could do with the resource limitations lifted. Especially if some of the classic superheroic gadgeteers got on the case. Imagine what they could do if the limits were lifted. Even your amazing do-good superhero could be persuaded by showing what a difference it could make