This is nothing new for airlines. Even a RT can be much cheaper depending on which way you start. I.E. I can book SFO-NRT-BKK r/t in BF for like $5500. I can book BKK-NRT-SFO in BF for $3400.
I can book them as one ways for $6000 ex SFO and $3700 ex BKK.


UA sees more $ and demand starting a flight in San Francisco than does it in Bangkok, Fiji, etc.
I wouldn't bet on the flight to AKL going down any significant amount.

UA may be getting in your way but I regularly find UA great for o/w fares. I have booked JFK-SFO for about $275 several times, MEL-LAX $750 two times and SFO-HKG for $550 all on fares that instantly allowed me to apply a R/GPU and upgrade from Y to J.
Compare that to trying to fly around o/w in Europe where Lufthansa or SWISS want $500 for a 90 minute flight.