I agree that the median has faults, especially when a particular demographic (like FHB) disappears from the market. However, until recently it was the best the ABS & others could come up with. What stat should we be using instead ? RPData have come up with the Hedonic Index which is an improvement over the median. It calculates the 'average' based on sales of similar types of houses. They release it towards the end of every month - see here.'Tis interesting that you agree that medians do not necessarily reflect the real world. Will you refrain from using it as a stat in future?
As an example of the flaws of a median - 200 sales of 3 bedders and 100 sales of 4x2 in a suburb would give a median skewed towards the lower end of the range. If FHBs disappear, there will be only 100 3x1 sales, but 200 4x2 sales - consequently the median will jump towards the higher end of the range. So the composition of the data has an effect of the median, even if every single one of those houses sold for exactly the same at it did in the previous period.
A Hedonic Index takes the 'characteristics' of the dwelling into account. As an overly simplistic example, it takes the average of 3x1 sales & the average of the 4x2 sales for each period, and calculates an suburb average based on those figures. FHBs disappearing from the market will have little effect that type of Index.
Most house price index data providers use the OSR data which is accurate, but several months after the event. RPData collect their data from various sources earlier in the house buying process and that gives more timely information.