"30p each or only 3 for £1" isn't a joke. I saw this in a London store when they tried making multi-pack offers near the checkout actually more expensive than picking up separate items.
"Meal Deals" are a fantastic scam that charge you more for eating less. If you don't take the crisps or drink it doesn't "count" as the meal-deal, and the individual items cost more. I end up buying an extra bag of crisps I don't want and giving it to the homeless person outside.
Like many British supermarkets they operate a three tier pricing structure, normal, discounted (with yellow labels) and "Clubcard" prices. These are applied to similar items on proximate shelves, so you're never quite sure which ones the offers apply to. Sometimes those little yellow stickers don't scan, and surprise.. you pay the original price.
And don't get me started on automatic checkouts, which are basically "mugging robots" designed to rob humans.
Supermarkets are playgrounds for screwing people over with little mind games. What a desolation of human life for those who waste their days thinking up this shit.