One way fare to Sydney from JFK possibly!!
 

Some help needed. DD and SIL live in New York City. SIL is about to start a Masters Degree at Sydney university, start date end July. In October DD may be doing a hotel gig in Busan South Korea.

Initially they were looking for the cheapest one way fare to Sydney, but they seem to be as expensive as a return ticket in some cases. If they did book a return they are not sure whether SIL would go back to New York or to South Korea to join DD!! If they book NYC and then want to change it would obviously cost more to change.

Just wondering if there are any tips on best way to approach this,

You might want to look at Cathay Pacific, which we have used to get from YYZ (Toronto) to Australia. Fares are competitive and change fees relatively low.

I would look for a one-way ticket to SYD, then worry about the Korea options later. I'm seeing one-way economy fares in the US$1200 range from NYC to SYD, which is roughly 1/2 of a return trip with a 120-day spread. So it's likely there's not much to lose by doing the one-way as opposed to an open-jaw or round trip.

Thanks eliz and Gardyloo

Will Australian immigration let you in the country without a return ticket?

He is a New Zealand citizen MissGreen so doesn't need need a visa. Might be different if he is coming from the US, worth checking out.