[WalterBright]

Here in Seattle, we spend $$$$ buying a tunnel boring machine, bore a transportation tunnel for a section, and then ...

... cut up the boring machine for scrap!

It's like setting up a giant printing press to print a newspaper, and then printing 10 copies.

[Tomte]

At least you're getting something back. When the channel between Dover and Calais was bored, one of the boring machines was simply left underground, because it would have been to expensive to retrieve it.