This map from HSH.com, a mortgage research site, shows just how insanely expensive some housing markets in the United States are. Per The Washington Post:

On a national scale, a buyer who puts 20% down would need to earn a salary of $48,604 to afford the median-priced home in America. But that total varies a lot from city to city.

The site's calculations assume that a buyer spends 28% of gross monthly income on housing, including principal, interest, taxes and insurance and makes a 20% down payment on a house.