Today I found this on McAfee's web site:
Now, why would anyone want to pay £79.99 (as of today $97.25) instead of paying $89.99???
This reminds me about the time when I had a pre-installed McAfee product on my hardware and before it would tell me how much it would cost it wanted all my personal information.
My guess is that there is a mistake in displaying the currency. Please post back the web link where you saw this offer.