Agreed often AKL-NAN-AKL sells for around $800-900NZD when its not on sale, so around $600-700US.

The Pacific Island's don't tend to full into the budget market ex-NZ,AU hence the airfares tend to match it. At the end of the day most of the Pacific Islands are monopoly routes, and at some point have an relationship with Air New Zealand. Even though a couple of the Islands have there own airlines, they tend to play nice with NZ.

Note with ex NAN the departure tax is around 100-150FJD, so that instantly makes up an large amount of the fare. Also then if your $300 fare on is on NZ make sure it isn't 'Seat Only'.