I've always been a little intrigued how our local Sainsbiry's handles special offers. For example, today, they had a special offer on Maltesers that worked out at 89.3p per 100g. A couple of shelves up from this they had a larger pack at £1.20 per 100g. Anyway I came up with a few guesses as to why the much more expensive variety was left on the shelves
I didn't find the right solution from the Internet.
References: https://forums.digitalspy.com/discussion/2219428/supermarket-special-offers-policies

Animated Video Example