I don't know if post-scarcity must mean perpetual motion machine. I'm not certain if you're familiar with the societal concept of systems collapse but it may be that attempting to do that would result in a maintenance burden that's untenable... Also I think a large chunk of NYC's value is in its people and I believe there's always going to be advantageous positioning from rarity, maybe this eventual society still has a government that has a capitol building and people congregate specifically around that... or perhaps it's more artificial - if the whole world was a city perhaps it'd get less significant and value would come from living at exactly 0' 0' or 3'14" 15'92" and so on.

I think there's a bit of innate petty jealousy in human beings so land value differentials will always exist.

But, that angle is pretty thin, so maybe I'm just stretching the argument at this point. Quite interesting to ponder!