That's a good price indeed HT - Harris Technology also have it for the same price $47.82:
Microsoft Windows 8 Pro Pack - product upgrade licence | ht.com.au
For sale to individual customers only. Limit of 5 units per customer.
Microsoft Windows 8 Pro Pack - product upgrade licence
It's Windows reimagined and reinvented from a solid core of Windows 7 speed and reliability. It's a touch interface. It's a Windows for devices. And it's easy to try - whether you're installing it for the first time, or moving from Windows 8 consumer preview.
This version upgrades existing machines with Microsoft Windows 8 to Microsoft Windows 8 Pro