I've lived 6 months in Tokyo, hard to read in my opinion. I did the same map for Paris two years ago http://www.smartloc.fr/carte-des-loyers-a-paris

I wonder why this map don't contain Edogawa. That city is cheapest in Tokyo Metropolitan Districts.

I think the focus was on the central districts where there's more variance on price, and so more utility in this kind of detail.