Um.. just checked Sim2 and Adelaide is only 61,000 value, Canberra 21,000, newcastle 5,000 and Gold Coast 36,000. Adelaide should be in the 100,000's, canbera around 80,000's and Newcastle at least 60-70 000:)
Are those the gate rental costs? Those numbers are not the city's population (although it is proportional). And the gate costs haven't been adjusted yet since the demand increase.