Who will pay the billions in additional costs for Stuttgart 21?

Deutsche Bahn, which is the official client of Stuttgart 21, currently estimates the total costs for the project at 9.15 billion euros and has also factored in a buffer of 640 million euros. However, a financing agreement from 2009 only regulates the distribution of costs up to a good 4.5 billion euros. At that time, the state pledged a participation of 931 million euros, the city of Stuttgart gave 292 million, the airport contributed 227 million, and the Verband Region Stuttgart pledged 100 million euros.