Why does a Creative Cloud subscription cost more in Australia?

No-one but Adobe knows.

Everyone but Adobe thinks it's unjustifiable but that hasn't stopped them charging what they like, wherever they like since they're a monopoly.

Geographical pricing differences is one of the most discussed subjects on this forum.

See this thread re: European price differences

http://forums.adobe.com/message/4408382

Microsoft, Apple and Adobe are being asked similar questions by the Australian Government

http://www.theage.com.au/technology/technology-news/it-giants-in-price-probe-20120428-1xs1 6.html