Interesting deal, but as always there are T&Cs:
Offer applies to return adult Economy, Premium Economy and Business Class airfares including Seat, Seat+Bag,The Works and Works Deluxe booked from Australia to New Zealand on Air New Zealand operated services. Domestic travel in Australia will be on Qantas airways. To obtain the $200 off return discount per adult, book online at www.airnewzealand.com.au and enter the promo code NZ200 into the promo code box for departures 7 Jan - 3 Apr, 1 May - 26 Jun 2019, with return travel permitted 14 Jan - 9 Apr, 2 May - 3 Jul 2019. All travel completed by 3 Jul 2019. Promo code must not be used in conjunction with any other airfare related promo code. Excluded booking classes are F,I,N,R,J,S,P. Final discount will be shown on the summary page of your booking. Baggage Allowances: For Economy Class, Seat+Bag and The Works airfares your first checked bag up to 23kg will be free and Works Deluxe passengers are entitled to two checked in bags up to 23kg each, with additional charges applying for additional bags. Passengers purchasing Seat Only fares are not entitled to a free checked baggage allowance, however bags can be pre-purchased prior to travel online via Manage Bookings or by phoning the contact centre (see rates and terms and conditions), or alternatively for a higher rate at the airport Offer valid for new bookings only. Paying for your booking with a charge, credit or debit card incurs a percentage based fee that differs by card type. Return government and airport charges may vary. A non-refundable service fee of $30 per person, per one way journey applies to Contact Centre bookings. Price correct as at 9 Dec 2018. Seats are limited and may not be available on all flights. Customers who purchase fares using Airpoints Dollars™ will be required to pay in cash, the government & airport costs. Prices may fluctuate due to exchange rate and tax movements. New deals may be released at any time. Airfares may be extended.
I did find some decent prices though, e.g. Sydney to Wellington return for 2 people for less than $450 return in early March! You might have to dig around but and I managed to find SYD-WLG return for $300 as well in early May - not too bad! All bargains listed are of course the cheapest fares (no seat + 7kg carry on, no checked bags)…
I need to go to Auckland in 2 weeks. The prices are so ;(