Your best bet is to see if there are any "all inclusive" deals. For New Zealand or South America for that matter, it might be hard to find a package. Still, those can be screaming deals. My friend got an all inclusive deal for the Yucatan Peninsula for $750. That includes, airfare, transportation to/from the resort, 3 meals a day plus alcohol. When he tried to piecemeal it, it was $500 for the airfare alone. I believe it's a 5 or 7 day trip. Of course the swine flu suddenly erupted after he booked and his trip might get canceled.
Anyhow, New Zealand will obviously cost more, but you might be able to save some significant cash by getting everything up front. Good luck.