He said these extra items are normally provided for any artwork gifted to the council, and relative to the size and scale of the project.
Some outstanding construction-related costs were still being negotiated with the contractor before the final cost will be known.
"We do expect these to be resolved soon, which will give us final project cost," Kimpton said.
Asked if the council and contractor are in dispute over construction costs, a council spokeswoman said as is typical towards the end of any contract, there are a range of issues and queries to be finalised before the final invoice can paid. These remain commercially sensitive, she said.
"The artist's work has been completed within the artwork budget, which amounts to the gifted $1.5m," Kimpton said.
The sculpture has been acclaimed by art critics and welcomed since its unveiling on Queens Wharf in February. It has faced artistic problems, public criticism and a tortuous council process.
The cost of the sculpture, based on a modest, two-storey Mt Eden state house, blew out to $1.9m thanks to plans for a Venetian glass chandelier depicting a glowing garden of native flowers, birds and insects.
But the budget was cut back to $1.5m when Parekowhai replaced the big light with a smaller installation that included a statue of Captain Cook and light installations representing the stars of Matariki, which guided early Maori navigators.