Qantas is offering return flights to San Francisco for $856. Lots of dates from January to September 2018. Fares includes bags, meals and seats. All flights stop in Sydney. The layovers can range however some go up to 12 hours which is great if you want to explore Sydney in the day.
Find the cheap fares on
ex Auckland - Google Flights - Skyscanner
ex Wellington - Google Flights - Skyscanner
ex Christchurch - Google Flights - Skyscanner