[welshman]

Basically what Mixer said.
It started if You remember with CoDMW (The first) which was selling on Steam at US$49 (About AUS$60 ATT and about AUS$89 retail). So what people where doing was, armed, with a printout of the Steam store page they would march into EB (and others) and demand that They beat (The US$) price under their "Beat any Price" policy ( I was there when someone acually tried this and it was hysterical to watch).
I had a Friend who worked in the local EB and She told Me that once EB and other retails cottoned on to what was happening they protested to Activision basically threatening a Boycott of ALL Activision products if Steam wasn't brought back into line and over night CoDMW went from US$49 to US$89.
If You also remember this too happened to Borderlands with the 30 dollar overnight hike.
I think the problem then got worse when Acti and 2K told Steam You must sell this for 89 Dollars in Australia........except they forgot to mention "In Australian Dollars" and thats why You are seeing the Steam price cost more after conversion than Retail price....I think it's the only way to explain why the Steam price is more over inflated.