btw. a lot of your questions are answered with a single statement.
The world biggest manufacturer is a really really small company, compared to a lot of other companies. The villages around the company have a smaller population (together) than the company has workers. (herrenknecht only tells about direct employed people, which is way below the people that work on-site)
the pressure from chinese companies is extremly big and a lot of tbm's are special machines that ONLY work for the specific tunnel/project, there is no such thing as an tbm for everything, most (not all) of them are special purpose tools.
> a lot of tbm's are special machines that ONLY work for the specific tunnel/project,
Yes, a lot, but not all:
> In December, the TTC bought a banner ad on the Tunnels & Tunneling International website, to list for sale four tunnel-boring machines it used to dig the 13.5-kilometre twin tunnels for the Spadina subway extension to York Region. The TTC had bought the machines in 2009 from Lovat for $58-million. Today the TTC has stored the machines at the Keele Valley landfill site. The machines are nearly good as new, the TTC says. “The TBMs are generally considered to have a useful life of tunneling of approximately 20 kilometres,” reads a TTC tender document. “At the completion of this project, they would have been used between 2.5 and 3.2 kilometres, or approximately 10-15% of their useful life. Accordingly, the TBMs will be capable of significant additional tunneling on other projects.”
