> There are also resources that are drawn from a fixed-size pot. Land ownership for example. If a tiny number of people assume possession of vast amounts of land, the amount left for everyone else is reduced.

Excellent point. Similarly, the pool of doctors is fixed in the short term, because it takes time for new doctors to go through medical school so that supply increases to meet demand.

This means in the short term, rising inequality can drive up the price of medical costs (at least the part of these costs that goes to doctors' wages).