Dublin's Metrolink has already racked up a bill of €300m despite construction still being years away.
The project was first proposed back in 2000 with planning permission for the Metro North line granted in 2011. However, the project was suspended due to the economic downturn and a new Metro North project was announced by the NTA in September 2015, with services due to commence in 2026.
Metrolink succeeded that project with services currently being projected to commence in 2034, meaning the underground tram system will be delivered 34 years after the project was first proposed.