About $15 million has already been spent on strengthening the Wellington Town Hall, even before construction has started.
But the city's mayor Justin Lester said it's normal for that amount of money to have been spent on designing and signing off on such an expensive project.
Earlier this year it was announced the cost of strengthening the hall had jumped for the fourth time, to at least $112m.
Since the town hall was closed in 2013 for strengthening, the cost of the project has gone from $43m, to $60m, to $90m.
The final price is expected to be higher.
The money spent so far had been on planning and design, Mr Lester said.
"We want to make sure that Wellingtonians get a good outcome, they want a strengthened town hall in a building that's going to be here another 50 to 100 years.
"That's why it's going to be base isolated. It is on reclaimed land, it's a category 1 heritage building.
"It's a complex project, that's why you have to invest in the planning and design up front."
Mr Lester said $1.6m of the spend also went on securing the building's masonry, as legally required.
Another $4.8m had been spent on design work and consultants on an earlier iteration of the project that was cancelled in 2014.