Avast Software has numerous modules/components that can be purchase extra $ on top of the yearly subscription cost for Internet security.
I would not be overly concerned as I also use/have used AIS for years and simply ignore the popups aimed at selling me a/more components I don't want.
For example: As a User of AIS< Anti Track Premium, Data Shredder, Webcam Shield and Driver Updater are some of the modules I don't want so no "added" cost to me.