I found it funny that it only allows you to disable it for 24 hr period and then its enabled again..
You didn't read far enough.
So, here is how to disable Avast SafePrice in Mozilla Firefox and Google Chrome
In Mozilla Firefox:Enter the following into your address bar: chrome://wrc/content/options.html
This gives you access to the “avast! Online Security Settings” screen.
Scroll down to the bottom and uncheck “SafePrice Receive SafePrice shopping recommendations on relevant sites.”
Click on the “Save” button.
If this add-on is not installed, nothing happens. Why it's on one computer & not another is unknown.