Probably just saves the money counting equipment? I don't really see how self service tills make shoplifting any easier.
Try weighing in a bag of mushrooms as potatoes instead and see how much you can save!
Scan a 'reduced label' item, then the packing area scales are turned off and you can load whatever you like onto the packing area.
De-code the 'reduced label' item and manually enter a different (lower) price (instead of scanning) to save even more!
1) comes from a friend who had just that problem in his grocery department - the stock said they had mushrooms by the pallet full, the shelf was empty. CCTV revealed all and the culprit was banned, my friend even having the banning letter available on-line in multiple languages.
2) comes from a local newspaper article where the lady was prosecuted for re-using the same 7p reduced label dozens of times on the same shopping trip then repeating the trick days later.
3) I am tempted to try by putting in a higher price than the label says, just to see what happens. Can I be prosecuted for deliberately over-paying for an item?