The Jetstar deals keep coming, and I’ve not seen it below $200 before to Queenstown.
The super cheap ones seem to be in March, but there are also deals in May/August.
I’ve found them via FlightScout’s search page (https://flightscout.co/au/cheap-flights/melbourne-australia-…) but the prices are actually even lower when you click through to skyscanner. Use whatever engine suits you better.
From: Melbourne TO: Queenstown, NZ
Bags / food are extra.