Earlier quoted context omitted.
The best way i've seen this framed is: in all of the US, there are only about 2,000 blocks of housing with sufficient density & walkable services to support car free living. This is some of the most sought after and expensive real estate in the country, but zoning codes won't allow more of it to be built. Example zoning restrictions: mandatory building setbacks, mandatory parking requirements, mandatory building sepa…
Manhattan alone is on the order of 2000 blocks, I don't know where you came up with that figure.
* Forgive my ignorance for being from the West Coast. Even in SF its difficult to live car free if you don't live on BART or Muni Metro.