Malwarebytes Premium seems to be offering 50% off their normal price of Aud$60 for one device. Even greater discounts for more licenses. Could be useful for a group buy of 10 licenses for two years which works out to just $18.60 for each license for two years. This is a pretty good deal for one of the best antivirus and antimalware products around.
Microsoft's inbuilt AV is not good enough and this is one of the cheapest ways (unless you have an .edu email address) to get one of the best products on the market.
Note: Coupon code is inbuilt into the URL.