For those who are interested here's some price info.
The cost of a round trip from Auckland to Sydney on a Bombardier Challenger 350 or equivalent which sits 6 to 10 passengers ranges from AUD ~$38,000–$53,000 for the round trip.
With 5 other friends that's around AUD7000 each which is a bargain considering how much more pleasant the flight will be. I can assure you it's worth every penny.
If you can negotiate an "empty leg" deal the cost drops dramatically. This arrangement is very common in the USA but occurs less often in the AU/NZ region simply because private jet traffic volumes are much lower. Nevertheless it does crop up periodically and the cheapest private jet trip from Sydney to Christchurch cost me only AUD2900.