I know of someone was recently trying to go Mt Isa to BNE. Was cheaper to do Isa to Auckland and throw away the last leg.
Quite often it’s cheaper to go the Australian Regional city to say BKK, DPS, HKG, SIN via Sydney return on one booking then it is a single domestic from regional to Sydney return.
Play with the multi trip booking system a bit and it’s why so many people in isolated communities plan a overseas holiday with a capital city visit.