The concert hall they refer to is the Elbphilharmonie which tripled its costs and construction time.
Costs for the tax payer are actually more than seven times (789M EUR) the original estimate at the time construction began (114M EUR in 2007). The initial estimate in 2005 was even lower, foreseeing costs of below 100M for the tax payer with donations supposed to cover the difference.
Thanks, somehow I had the wrong number remembered.