Jetstar offers $88 one way flights from Queenstown & Wellington to Gold Coast, Australia and from Christchurch to Sydney, Australia. Flights are for May 2015. A return flight to Gold Coast comes up around $~290 and a return flight to Sydney comes up around $250. You could always chance it and just book the one way and wait for a Jetstar Australia-NZ sale.
Thanks to Shaw for the heads up.