[woodruffw]

$2.5 billion per mile of tunnel, not track, on the SAS project[1].

(This is an outrageous number, but it's not a "true" benchmark for what a mile of subway construction costs in the city: similar crosstown construction in Brooklyn or Queens, which badly need new lines, would be significantly cheaper due to both lower density and the possibility of cut-and-cover instead of tunneling. Plus, no steam pipes in the way.)

Edit: for comparison, the IBX is expected to cost around $400M per mile[2]. Which is also obscenely expensive given how much of the right-of-way exists, but demonstrates that there's no clean apples-to-apples comparison here.

[1]: https://www.bloomberg.com/news/articles/2023-02-23/in-nyc-su...

[2]: https://www.etany.org/interborough-express