My impression from reading the BestFlights site is that this is one of the shorter Circle Pacific fares, not the 29000 mile one which is the only one which can be used to go the S America (see rules extract above).

There are two other fares, allowing maximum mileages of 22000 and 26000.

From HKG the CX published retail prices are:

22Y: 20180 22J: 33740 22F: 48180
26Y: 24620 26J: 41160 26F: 58780
29Y: 26240 29J: 43860 29F: 62630

At current interbank rate, that makes the 29Y bought in HKG AUD5839, and the 22Y is AUD4490 (compared to whatever BestFlights is offering being AUD2749).

Thus proving the point that HKG is a stunningly expensive place to buy air tickets.