Announced on its Windows blog, Microsoft will be making the upgrade available at that price for 131 markets. It doesn't specify if Australia is one of those, but it's highly likely — as Gizmodo Australia pointed out, Australia already qualified for the US$14.99 upgrade for new PC buyers.
During the upgrade period, you can add Windows Media Center for free, through the "add features" option. Media Center has been removed from Windows 8's main package and has been implemented as a standalone, paid product, with Microsoft citing poor adoption.
To upgrade, a user just has to hit Windows.com, and follow the Windows 8 Upgrade Assistant. At the end, they'll get a choice to create an ISO or create a bootable USB stick. If necessary, a backup DVD can be ordered from Microsoft for US$15.
US consumers can pick up the physical DVD upgrade in store, for US$69.99, although we're still waiting on Australian costs.
The promotional price and free Media Center option are only valid until 31 January 2013.