you forget that their supply chain is greatly reduce, we doesn't know how much minerals and energy (and activities for pops in a less extend) are consume to get consumer goods and services (still gesalt empire have a "maintenance" value to keep high but it's less demanding than services).
On the other hand, you don't have commercial value (and so energy mainly) which can skyrocket has the time goes by.
On the other hand, you don't have commercial value (and so energy mainly) which can skyrocket has the time goes by.