From my following of its projects over the past two decades, it appears to me that DB spends an awful lot of time and money on planning, yet those plans remain remarkably resistant to changes reflecting the development of technology in the meantime or the consideration of even the most obvious potential problems. Hatchets down, to battle stations. For example, while building lines for 350 km/h is now more or less international standard, DB claims it would cost too much to re-model its decades-old plans for 250 km/h lines.

The cost of tunnels when actually built is also high than in some other places, which is even more remarkable given DB's reluctance to build bi-tube rather than two-track single tube tunnels, and its criminal cost saving on escape shafts and cross-connections. Dealing with geological challenges is another thing ().

City-crossing tunnels with subterranean platforms below the old main station for long-distance and high-speed trains aren't something unprecedented, either: Antwerp already has one, more are in construction in Madrid, Barcelona, Bologna, Firenze. AFAIK none of them cost nearly as much as Stuttgart 21. Such a project needs good organisation -- which the Stuttgart 21 project doesn't have at all.

Maybe DB needs foreign expertise?

As a final note: there is another project of a new through station that seems more a real estate project in disguise, though at least without subterranean platforms: Vienna's new central station. That one is constructed full-throttle. But it will be a funny 'central station', without a subway link...

_{*Lunatic*, n.
One whose delusions are out of fashion.}