This deal was for World Backup Day, and despite saying that it ended 31st March, I successfully signed up for the family unlimited plan today. CrashPlan have Australian data centres and upload speeds have been great.
Here's a cost breakdown of plans:
Unlimited Backup for 1 PC - $60.50 (usually $92 monthly / $69.30 annually)
Unlimited Backup for 10 PCs - $129.80 (usually $198 monthly / $165 annually)
So the 40% off is from their monthly plan, but still represents a great deal.
Also note that the cart will show prices ex. GST until final checkout.
Not bad, but I'm sure I paid around $200 for 4 years for 10 pc's a couple of years ago.
Great service though.