What is the average salary of assistant professor in New Zealand?
You can find the current collective agreements for all universities on the Tertiary Education Union's website. Entry-level salaries for a lecturer, and the low point of the senior lecturer range, at the start of 2021 were as follows (all NZD):




University
L1 salary
SL1 salary




Auckland
83,602
106,285


AUT
73,966
91,226


Waikato
77,402
95,883


Massey
74,478
93,335


Victoria
79,276
99,870


Canterbury
79,671
102,142


Lincoln
73,018
92,723


Otago
82,416
103,678




The average is about NZ$78,000. These generally have annual percentage adjustments built in, so the base rate increases each year. There is generally also an automatic progression within a grade for current staff across several steps spread between the lecturer base and senior lecturer base, and it is generally possible to be appointed mid-grade as well according to experience (e.g. working time since PhD). All of this varies from school to school, and there are also other payments that may apply, so you should check the agreements for particular details you're interested in. If you're not a union member these rates will generally apply to you when you start as well (by law, historically, but the situation may change).
A couple of the agreements linked above have expired, and may have been replaced but not yet made available on the website, and some contain increments that hadn't come into effect yet. The general area of the numbers is right, though. There is a fair amount of variation between institutions, particularly the largest and smallest universities. There's also quite a bit of variation in how the scale works above that lowest-level entry point and how many steps there are (between 6 and 9 before moving to SL).