1. JB Hifi
The most you pay is around $25 or just under 15 EURO, however, they have heaps of specials. This store is something of a Melbourne phenomena that has spread across the nation. Basically, they undercut the price of most other stores (which retail for more like $30 or 20 EURO per CD). The stores present themselves as a 'bargain basement' with signage and prices sketched on the back of paper bags stuck to walls.
Not as wider range but nothing over $10 AU which is I guess about 6 EURO. They have pretty much the entire Bowie catalogue going for that price.
The only online store I use. I don't find it that cheap because like all major online stores, shipping to Australia pushes the costs up considerably. So the verdict is that if you're on a budget in Australia, then the 'real' retail outlets remain.......until they finally launch Amazon Australia.