Supernatural will be officially released in the USA on the 10th of September. If you have purchased this on the net prior to that date sorry you have been ripped off its pirate junk probably chinese. If you want the official release for around $52 (Amazon current USD price $39.96 + $6.48 shipping) depending how the aussie dollar is going.
Although as they have not been released as yet it can not be 100% certain but being a Warner Brothers release and going by all earlier Supenatural seasons these discs will play in Australian dvd players without any problems
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when no pricing has been confirmed anywhere else. Plus, the earlier seasons have been going at 12-20 bucks in blu-ray on other sites such as ozgameshop you can't really call this a bargain.