Tunnel boring is actually not that expensive, for some projects the raw tunnelling isn’t a big portion of the overall cost. I think for crossrail in London (whi

Tunnel boring is actually not that expensive, for some projects the raw tunnelling isn’t a big portion of the overall cost. I think for crossrail in London (which includes a fair amount of tunneling ), the tunneling is 10-20% of the total Prüfer cost. A large amount of cost is in the stations. In the us, a large amount of cost is inefficiency, projects cost much more than elsewhere, even considering purchasing power parities. Alon levy has written and talked about it extensively, e.g. https://pedestrianobservations.com/2019/03/03/why-american-costs-are-so-high-work-in-progress/ https://pedestrianobservations.com/2019/03/03/why-american-c...