When I first came across the listing for the game on Xbox.com I was confused by the price — was this just the original release? I purchased it for myself, but I have no idea where my Xbox 360 power cable is to verify. Finally I stumbled upon a stream from Twitch user Gtchy1230, who confirmed the 720p version he was streaming was purchased from the Marketplace for $US3.74.
It's a very odd price, which leads me to believe it's either some sort of mistake or a limited-time promotion, so if you're interested, now's the time.
UPDATE: Apologies, this story shouldn't have been published on the local site. The deal is not available in the Australian region. See this comment for more details.