It's another victim of Cost Disease: https://slatestarcodex.com/2017/02/09/considerations-on-cost-disease/ https://slatestarcodex.com/2017/02/09/considerations-

It's another victim of Cost Disease: https://slatestarcodex.com/2017/02/09/considerations-on-cost-disease/ https://slatestarcodex.com/2017/02/09/considerations-on-cost... >The first New York City subway opened around 1900... it suggests costs of... $1-4 million per kilometer... inflation-adjusted equivalent of $100 million/kilometer today... a new New York subway line being opened this year costs about $2.2 billion per kilometer, suggesting a cost increase of twenty times...