Melbourne Cheap Suits
There are lots of discount places that provide suits at very low prices. The one that seems to always provide $99 suits is ManToMan on Elizabeth St in Melbourne. The suits around $99 seem to be on the bigger, however for an extra $50, you can really get a decent suit. Business shirts also seem nice and attractively priced at $15.

SydneyCheap Suits
In Sydney, Fairfield seems to be the cheap suit area.