You could make the same arguement without any sci-fantasy. Why bother starting a new gold mine? If it doesn't have any gold then it's wasted effort, and if it has tons of gold then it will just depress prices. So why bother exploring for any resources anywhere?

Instead consider a big hunk of asteroid mined gold sitting in orbit. Free storage, and quick delivery to anywhere in the world. Park it up there and drop pieces of it when the prices are high enough.