Cost by distance is reasonable for talking about construction (the supply side). See
https://pedestrianobservations.wordpress.com/2011/05/16/us-r... for an overview. Even $125m/mile places the project a little high on that list, among mostly-tunnel and all-tunnel projects, and $1b/mile is in the WTF zone.
Cost by passenger or passenger-trip is reasonable for talking about utility (the demand side).
Cost by distance is reasonable for talking about construction (the supply side). See https://pedestrianobservations.wordpress.com/2011/05/16/us-r... for an overview. Even $125m/mile places the project a little high on that list, among mostly-tunnel and all-tunnel projects, and $1b/mile is in the WTF zone.
Cost by passenger or passenger-trip is reasonable for talking about utility (the demand side).