These comparisons appear to miss the biggest issues. The NYC Second Avenue subway involves extremely complex construction in a location surrounded by other subway lines and infrastructure. The Los Angeles subways examined are extremely deep underground in a rocky and seismically unstable situation. In all of these cases there were extreme challenges unlike those found in other cases.
Note that the Second Ave subway had been proposed and discussed for around one hundred years and was consistently considered too challenging to be practical. Doesn't it make sense that a situation like that would be extremely expensive to eventually deal with? Does finally building a subway line that for one hundred years was considered out of reach really compare directly to the construction currently or recently happening in other countries?
London's Jubilee and Elizabeth lines were extremely complex and threaded through other subway lines and infrastructure. They too were on the drawing board for decades, and in the case of the Jubilee line, did not start until a new boring technique called the bentonite shield was invented. London should be in the same ballpark as New York but the article suggests it is 3-5x cheaper per mile.
Complex projects in places other than NYC don't seem to have the same extreme level of superfluous labor that drives up the costs.
"The unions and vendors declined to release the labor deals, but The Times obtained them. Along with interviews with contractors, the documents reveal a dizzying maze of jobs, many of which do not exist on projects elsewhere.
There are “nippers” to watch material being moved around and “hog house tenders” to supervise the break room. Each crane must have an “oiler,” a relic of a time when they needed frequent lubrication. Standby electricians and plumbers are to be on hand at all times, as is at least one “master mechanic.” Generators and elevators must have their own operators, even though they are automatic. An extra person is required to be present for all concrete pumping, steam fitting, sheet metal work and other tasks.
In New York, “underground construction employs approximately four times the number of personnel as in similar jobs in Asia, Australia, or Europe,” according to an internal report by Arup, a consulting firm that worked on the Second Avenue subway and many similar projects around the world."
Note that the Second Ave subway had been proposed and discussed for around one hundred years and was consistently considered too challenging to be practical. Doesn't it make sense that a situation like that would be extremely expensive to eventually deal with? Does finally building a subway line that for one hundred years was considered out of reach really compare directly to the construction currently or recently happening in other countries?