Hi Rolf, I use Sydney prices as a barometer to guage other cities. For example when Perth's median exceeded that of Sydney I called "Perth bust"......and it did for a few years thereafter.
The CG used to go thru that boom-bust thing with monotonous regularity but I think it has become a bit more mature as a market in the last 15-20 years. (but not sustainable if it exceeds Darling Point / Elizabeth Bay / Double Bay / Mosman)
I've used Scott Durrant from Successful ways http://successfulways.com.au/ and very happy with the service. Not sure if he specialises in Eastern Suburbs but a phone call wouldn't hurt.