Recent research shows that city size can be used as a predictor for many of its socio-economic attributes. Recent work has also found that as Australian cities have grown, so has their income inequality. Census data for the Significant Urban Regions (SUAs) of Australia demonstrated that the larger the city population, the proportion of highest income earners aggregating in that city is disproportionally higher, whereas the proportion of income earners in the middle and lower categories is only proportional or lower than proportional. In this paper, we examine the scaling of the numbers of people in Australian Bureau of Statistics (ABS) defined rent and mortgage classes against city size, and find the same trend echoed: highest rent and mortgage payers accumulate disproportionately in the largest cities of Australia. This trend, coupled with qualitative observations on rising housing prices and affordability pressures in large Australian cities, raises concerns on how the economic and social quality of life in large urban areas may be preserved/raised for all sections of society, as opposed to only the highest earning brackets. In this paper, we present a reflective and critical analysis of the main causal mechanisms of why such a scaling may be becoming a stable trend for Australian cities. We then present some urban planning strategies that may help to counter such inequality producing mechanisms. Larger economic forces, beyond the reach of planning, play a large role in the production and maintenance of economic inequality in large cities. However, this paper specifically focuses on what urban planning can achieve given the constraints set by the wider economic geographic environment in which urban areas are situated.