According to an analysis by AUT downloadable on this webpage (pdf) in respect of total rates collected by the predecessor councils and then the “super-city” in 2011 :-

“[There were] annual increases of between six and 12 percent
from 2003 to 2010, but a more significant change from 2010 to 2011, when total rates received (excluding water and wastewater) increased 16 percent from $1,161m to $1,343m.”

This confirms what I have been saying: the creation of a Wellington “super-city” won’t save money; it will incur a lot of expenses that will require a rates increase and rates won’t go down thereafter.