I mean, Perth installed a rail link in the last five years to the airport. It also costs $5.20 to travel 100km from the airport (if you buy a cash ticket - cheaper if you get a smartrider card).

Melbourne has been talking about it for 60 years, they just can’t seem to prioritize it over whatever else the government spends money on. The airport itself has at various times been an impediment to the station as well, though. Much of the debate appears to stem on whether to make a subway or go above ground (cheaper).