In my opinion yes it is. Although the cheapest price i can find is around $19 a year.
4,274,588 population for 2007.
In 2006 3,200,000 people were connected to the Internet that's 74.9 % of the population.
Several premium .co.nz sites have also sold on Sedo recently for between 5000 and 10,000 USD.
New Zealand Sites (.co.nz) also show quite often in Google Australia.
There are many High Premium One Word Domains still available, as well, i think alot of members here really underestimate the online market in New Zealand.