This article found that on average we pay a little over $300 per month to live in a walkable neighborhood.
That tells me that demand is high and supply low. Why not build more of these places? Until the price gap levels out it makes no sense.
Also, the cost of walking is free. The cost of gas is going up, up, up.
Alas, economic recovery statistics still measure the economy based on housing starts. If people are paying the premium to live in cities, instead of suburban homes being foreclosed on, at which part of the economy should we really be looking?