When economists say A is scarce people misunderstand that supply of A is fixed. In fact this misunderstanding lies at the core of mistrust of capitalism.
What economists mean when then say A is scarce is that, a copy of A can be of utility to only a fixed number of people.
There is a lot of difference between the two understandings. One grain of Wheat may be of utility to only a fixed people, but its supply can be increased by agriculture. e.g. Some people even grow wheat in desserts and space.
I think the only thing that is truly fixed in supply in this universe is enthalpy. But even that could change in a googol years before the heat death of this universe.