Not the all-time lowest price (which is $1US cheaper) but still a pretty good price for those of you who want to play this game in the foreseeable future.
I do not think anything needs to be said about this cult classic game.
There was a user on Ozbargain who asked for sales on this for his kids - I cannot remember who it was but if you can please try to message him as soon as possible as this deal only lasts until 3am tomorrow morning.
Enjoy.
Note: the following is also on sale:
Age of Empires II HD + The Forgotten + The African Kingdoms + The Rise of the Rajas for $11.80US (~$15.59AUD):
https://store.steampowered.com/bundle/2149/Age_of_Empires_II…
That's a bit of a stretch. The water looks better and it plays widescreen, otherwise the graphics weren't really updated.
Still a great game though and good value at this price.