Justin Fox:

That said, the U.S. probably also ought to be spending less on infrastructure. Not overall, but on something like a per-mile basis. Broad international cost comparisons across all kinds of infrastructure don’t seem to be available, but there is a growing body of evidence on one particular infrastructure area that matters a lot to me as a New York City commuter: subways and other rail systems. And it shows that U.S. construction costs are among the world’s highest.
 Transportation blogger Alon Levy has probably done the most to raise awareness of this, with five years of posts documenting the cost differences. And last year, Tracy Gordon of the Urban-Brookings Tax Policy Center and David Schleicher of Yale Law School examined 144 planned and finished rail projects in 44 countries and found that the four most expensive on a per-kilometer basis (and six of the top 12) were in the U.S.
 To put these numbers in global perspective, New York’s Second Avenue Subway will cost roughly eight times more than Tokyo’s Koto Waterfront line and 36 times more than Madrid’s Metrosur tunnels on a per-kilometer, purchasing power parity (PPP) basis.
 Why is this? It’s actually pretty hard to answer. Here’s Levy, writing in November 2014:
 I try to avoid giving explanations for these patterns of construction costs. If I knew for certain what caused them, I would not be blogging; I would be forming a consultancy and teaching New York and other high-cost cities how to build subways for less than $100 million per kilometer.
 Still, others have been willing to offer explanations. In a 2012 Bloomberg View piece, New York land-use and transit writer Stephen Smith blamed over-reliance on outside consultants, overly ambitious station architecture and a legal system that favors contractors over the agencies paying them to build things. Gordon and Schleicher agreed that the legal system may be an issue, but for other reasons: