Housing is cheaper in Perth because it's isolated from the rest of the country. The only people who emigrate to Perth are those who are priced out of Brisbane, Sydney and Melbourne.
People who were priced out of Brisbane and Sydney are the nucleus of Perth's RL community. The majority of Western Australians will never support rugby league.
Brisbane has a very large RL fanbase spread across all classes and demographics. The game is a minority sport in Perth and confined to expatriates who were priced out of Brisbane and Sydney. Perth RL's main cheerleader is a soapdodger from England. His puppet is an expatriate from Sydney.
It's fanciful to think Perth will ever have a sizeable RL community that's comparable with Brisbane and Sydney.
Wait so it's full of people from Brisbane and Sydney who can't afford to live in either city, but also those people wouldn't support rugby league despite coming from cities that you describe as being "spread across all classes and demographics"? And you don't see how that is poor logic?