Melbourne is a positive outlier and not at all representative of the rest of Australia. Finding senior devs in Brisbane is an insanely arduous process and its not uncommon to see positions take 6+ months to fill (at least at the places I've worked at). Even when companies start throwing money around like crazy, the talent just isn't there.

I've heard that Sydney isn't so great either. Once devs hit seniority they run along to join a hip Melbournian startup, get gobbled up by Atlassian, or just migrate to Silicon Valley.