Your mistake was thinking that I, the corrupt landlord who pays bribes, cares about a macro analysis of every all the properties, or that some analysis about the current distribution of incomes and possible rents will stop me from doing exactly what you say is impossible. I don't own every property in the city, especially the ones that aren't built because I capture zoning, so arguments about average GDP and average rent and whatever else do not stop me. Your analysis is useless.
This is the only feature that's relevant. If productivity goes up, you can charge more. If it does not, you cannot.
You may do some corruption or some zoning or some whatever else you want, but at the end of the day, if productivity goes up you can charge more and if it does not you cannot charge more.
Hope that clarifies!