Hmm... according to EF:
DONE4 exMEL - A$10 189
DONE4 exAKL - A$9 623
Unless you actually intend to be in AKL - I don't see much different in costs? I mean - you'll need to factor in the costs involved like the transtasman flights, accommodation (should you need to allow a day to pick up the tix), not to mention the hassle of dealing with a reservation office in NZ.