> "1. People have wildly incorrect intuitions about where land value is concentrated"
Fwiw this sort of land value gradient has been studied in economics for ages. See papers on monocentric city model, going back to Alonso (1964), Muth (1969), and Mills (1967). Or even further back, von Thünen was talking back in 1826 about how land values spike as you get closer to the marketplace.
Land and "improvements" are assessed separately, and I believe this is plotting just the assessed land values. In the small text about each map, it says to use the settings to switch to full assessed value or improvements. But still, it's very hard to actually assess land value in an area like Manhattan where there are basically no land-only transactions