Unethical Life Tip: Find a nice expensive steak in the supermarket and go to the fruit section and weigh it as the cheap apples; pop the ticket barcode over the steaks barcode. When you go to the self service checkout scan the steak and pop it on the scale. The steak weight will match the barcode scan weight and it will look like you scanned the item to the security camera.

Consider the saving as your payment for doing the supermarkets job for them...

Alternatively do the first steps and pop the steak back in the fridge to pass on the saving to another customer.