Earlier quoted context omitted.
I really wouldn't trust 'picked up off the shelf' detection, not without the whole thing looking like a giant vending machine. RFID tags on products probably works better.
RFID probably works better if you control the packaging, for instance, for deli counter products. But for packaging that you don't control, you either have to slap an RFID tag on when the items get to the store, negotiate with suppliers to start to include RFID tags in their packaging for items shipped to your store, or arbitrarily limit yourself in terms of which products your store may sell. Not to mention that, if…
That's already handled in grocery -- people can mess with regular barcodes if they want. it's a known cost of business