What are Melbourne's most expensive suburbs?

It depends but here is my take:
Traditional Melbourne power suburbs: Toorak, Brighton, Canterbury
Desirable for professionals: South Yarra, Hawthorn, Kew & Caulfield North
On the Mornington Peninsula; Portsea, Sorrento and, of course, Mount Eliza!

toorak, sy, balwyn , kew , canterbury, hawthorn, brighton off the top of my head..

Toorak and Canterbury are by far the top two most expensive suburbs. This hasn't changed much since the 25 years (at least).

Toorak, Kooyong, Deepdene, Canterbury, Brighton, Hawthorn, Kew, Malvern, Balwyn, Camberwell, St Kilda West, Albert Park, Middle Park, Glen Iris, Surrey Hills, Elsternwick

kevfev has created new discussions on Melbourne's $20 million homes on http://www.streetadvisor.com.au/melbourne-greater-victoria/questions/melbournes--million-homes and also Melbourne's most expensive streets http://www.streetadvisor.com.au/melbourne-greater-victoria/questions/melbournes-most-expensive-residential-streets