Virgin Australia are offering return flights to Hong Kong (via Melbourne) from Auckland for $756. Fares include meals, seats and bag fees. Book directly with VA.
Seems inline with cheap fares to HK on full service airlines.
Via Scott's Cheap Flights(scottscheapflights.com)
Is it possible to add a stopover in Melbourne?
Can't seem to add a stopover. The alternative is find your own cheap return flights to Melbourne, then book seperately to Hong Kong on Virgin. They are running the same deal from Melbourne for $435 AU Return(ozbargain.com.au) (~$470 NZD). So you just need return flights under $300 to match.
Maybe Virgin can help if you call them up.
Man that is cheap!