I recently ordered MCPD Self-Paced Training Kit (Exam 70-547): Designing and Developing Web-Based Applications Using the Microsoft .NET Framework from Amazon and it cost me about $AU 60 (including postage).
MS Press have just launched their Australian web site, and the same book is listed as $AU 120. Dave Glover mentions that user group members can get a 50% discount, but only for this month. So for this month at least they are comparable.
It isn't just MS Press though. I've seen other Australian booksellers listing this same title at equally uncompetitive prices. About the only reason you'd buy local is if you didn't want to wait a couple of weeks for Amazon's standard delivery to arrive.
Certainly, the Australian dollar is very high at the moment, so that helps with the exchange rate, but I still don't get why there's such a huge price difference.