As mentioned previously, the "estimated value" of my properties dropped back towards more realistic values this month. It's best to view the trend data in a plot of prices over time to spot any such "spikes" or "dips". Nearly every suburb has areas with a few unusually expensive houses (water views or large blocks that can be sub-divided), which push up the median sales price when several of them get sold in a month. Similarly, sales of a new release of "town houses" will push the median sales price down for the month that a development is completed.
Overll the price plot shows that the housing bubble seems to have finished "bursting" in the suburbs where my properties are situated - I now expect that prices will track between the inflation rate (~3%) and the typical long-term rate of house price appreciation (6%) over the next few years.
New housing construction has been below demand for the couple of years (see previous post here), so I expect some upward pressure on prices to appear in 2-4 years time (the start of the next "boom").
This chart from Quartile Property [link] shows the past 25 years of median house prices in Sydney including two market peaks seen in 1989 and late 2003.