[throwaway27727]

It also ignores the vast differences between densely populated and not very populated cities.

[endisneigh]

Even Manhattan is cheaper than most places according to the same metric.

[brewdad]

Many apartments (condos in the rest of the country) in Manhattan are structured as co-ops with huge monthly obligations. The sales prices are lower because you can easily be committing to $2000 a month in payments to a co-op board. The total monthly outlays bring the numbers back in line.