"Council would be up for $4.7 million up-front, as well as ongoing costs. There certainly is a cost to the ratepayers," Mr Halse said.
"Then after four years it reverts back to the ratepayers, that should set off a whole lot of question marks."
No matter what happens to the building, the council has to "earthquake strengthen" it at a cost of at least $1 million.
Prosper Northland spokesman Barry Trass said he found Mr Halse's $2.8 million and $4.7 million claims "dumbfounding".
"There are no hidden costs to rate-payers.
"There is a buffer of $1 million for contingency costs [for the construction of the centre].
"We've covered operating costs for four years."
After four years, the council would become responsible for the building and its use, and could terminate the agreement with the Hundertwasser Foundation in Vienna and return the art.
WDC group manager for district living, Paul Dell, has recommended in the agenda for tomorrow's meeting that council include three options for the site in the draft 2015-2025 long term plan: The Hundertwasser Wairau Maori Art Centre proposal, the Harbourside proposal, or to demolish the Harbour Board building completely.
The Harbourside proposal, whose backers include former councillor Wally Yovich, would house Whangarei Art Museum, support the development of the Hihiaua Cultural Centre, and feature extensive landscaping, including a slope down to the river, visual connections, and an area suitable for Christmas in the Park and other outdoor events.
"One had work done on it for seven years, and one's had two months, I don't think that's fair," Mr Halse said.
He'd like to see a decision made in tomorrow's meeting, instead of it being pushed out until next June.
"We said we'd make a decision on October 29.
"I was prepared to make a decision then.
"This is going to drag on for another seven months and we will not be able to make a decision then either.
"It's not on. Our ratepayers deserve better than that. [They] are sick and tired.
"Surely we can make a decision and stop splitting our community."