The entire Universe is a resource. Sure, resources are finite. But it will be billions of years before we run up against that limit. Until then, it's just a cost/benefit kind of thing.
Speed of light is limited. So even in a infinite universe, you'll have to wait a bit to get the desired amount of the thing you want if you have to fetch it by yourself. So people might have to buy some to their neighbors if they don't want to wait.
Also, heavy elements in the universe are pretty scarce.