http://www.gizmodo.com.au/2012/05/apple-launches-free-app-of…
Looks like Apple is rolling out a free app of the week with "Cut The Rope: Experiments" being the first - http://www.ozbargain.com.au/node/70857
Usually promotional pricing on iOS or Mac apps are up to the developers or publishers.
Hopefully Apple's promotion continues to choose good apps.