How does average construction worker pay in Bay Area compare to Germany/Switzerland?
I also would be very surprised if the Germany/Switzerland were "outsourcing" the job to Chinese companies like the US does with big infrastructure projects. I mean everybody who ever dealt with outsourcing up close knows what in reality it is completely opposite to "cost savings", instead it is a way to "digest" even more money than it would be otherwise.
You have to remember that tunnel jobs are almost always run by a municipality which means that they're almost always union. I would imagine it is similar in Switzerland.
Tunneling is a niche industry and commands a high price.
Also, comparing salaries of those countries is just ridiculous, as Swiss salaries can be 2-3x higher on average than the German ones.