I would actually challenge that they are overpriced. From AKL, yes, maybe. But that's because to those destinations there's really no competition. Can you really compare a non-stop to LAX on NZ vs a stopover in SIN on SQ, adding hours to the journey?
For routes where they compete heavily, NZ pricing is comparable to the competition. J r/t from BNE/SYD/MEL to LAX can be had for less than $6k - rarely can you get an SQ or UA fare for that!