Sure a commute 40 miles each way will increase in cost from $5.33 to $13.33. But $8 seems hardly a concern when you are wasting 1.5 hours a day driving.

Cheap energy is certainly necessary to create sprawl, but it isn't the only thing. Rather urban areas are often downtrodden in the US. Take a look at San Francisco, a pretty nice place by big city standards; compared to its suburbs, it has worse transportation infrastructure, worse schools, more congestion, more noise, more expensive, more danger, more pollution. The benefits win out in my 20s, but I sure wouldn't want to raise a family there.