Similar to harm charge, depletion charge presents an opportunity to internalize an externality.  In this case, the externality is the consumption of finite resources.  Depletion charge presents an opportunity to incrementally increase the economic cost associated with the use of a finite resource by factoring in scarcity.  That is, using the next amount of a finite resource would be increasingly expensive to disincentivize its ongoing use.  This incremental charge does not need to be linear, and could itself increase with ongoing use of the finite resource, rapidly leading to a price that is cost prohibitive, rendering that finite resource economically infeasible.