Why the "cheap" item at the front is never the deal
A known-value item is a product shoppers remember the price of. UK supermarkets put those cheap — milk, bananas, a pineapple by the door — so the rest of the store inherits the feeling. The till does not.
EVERY PRICE HAS A JOB
Updated 13 September 2026 to add the UK legal unit-price rule, loyalty-price caveats, and source notes. Illustrative shelf prices are labelled as such.
There's a pineapple by the door of almost every big supermarket in Britain, and it costs about a pound. It is not there to save you money. It is there to answer a question you did not know you were asking: is this store cheap? You clock the pineapple, the answer feels like yes, and every price you see for the next forty minutes gets the benefit of the doubt.
Retailers call these known value items — the short list of prices shoppers actually remember. Milk. Bananas. Beans. Bread. Get those famously low, put them where everyone walks, and the whole shop feels cheap. Whether it is cheap is a different question — and it is the one this post is about.
The decoy at the door
A loss leader is a product sold at little or no profit — sometimes below cost — so you walk in. The loss is recovered on items you were never comparing: sauces, snacks, cleaning products, the "convenient" pack of grated cheese. Economists have described the tactic for decades. UK grocery is simply very good at it.
The placement is the tell. Bargains live at the entrance and on the end caps — the shelves facing the aisle — because those are the spots your eyes cannot miss. End caps are paid real estate inside the store. Nobody puts their worst deal on a pedestal.
The Competition and Markets Authority has, across several groceries updates, found the same pattern households already feel: Tesco, Sainsbury's, Asda and Morrisons are often dearer than Aldi and Lidl on a like-for-like basket, even when a handful of famous lines look competitive. A cheap banana does not make a cheap trolley.
"A supermarket doesn't need every price to look cheap. It needs about twenty."
What known-value items actually are
Shoppers cannot remember tens of thousands of prices. Academic and industry research keeps landing on the same range: people reliably recall a couple of dozen groceries, and use those as a shortcut for the whole store. Retailers price that shortlist aggressively. Everything else can drift.
In Britain the shortlist is boring on purpose. It is the stuff you buy weekly and mention to friends:
If your mental picture of "cheap" is built from those twenty items, the store has already won the argument before you reach the middle aisles. The fix is not to boycott the pineapple. It is to stop letting it speak for chicken, coffee, detergent and the rest of the list.
Where the margin hides
If the door is where prices perform, mid-aisle is where they earn. Across the chains we watch, the patterns repeat:
Add it up and the effect is bigger than most people guess. When we rebuilt the same 28-item family basket as a one-store shop versus a Groceria split, the gap between the dearest path and the cheapest honest path came to £13.40 on one week's shop. That figure is illustrative — your list will differ — but the direction is consistent: the door deal never closes the gap.
| How you shop | What you see first | What the till does |
|---|---|---|
| One big store, no list | Pineapple, berries, "2 for" end caps | Margin recovered mid-aisle |
| One discounter, whole shop | Genuinely low staples | Still miss items cheaper elsewhere |
| Split basket, unit prices | Nothing theatrical | Typical 10–20% off the same items |
The only number that matters
Every trick above survives on one confusion: the shelf price is not the price. A £3.20 punnet can be dearer than a £3.35 one if the packs differ by 50g. The number that cuts through is the unit price: pence per 100g, per litre, or per item.
In Great Britain this is not a nice-to-have. The Price Marking Order 2004 requires most retailers to show a unit price on pre-packaged goods. It is printed small, often in a corner, and routinely ignored. That is the whole game.
Once you read shelves this way, the spell breaks. The door pineapple is still a fine pineapple — but it stops speaking for the other 27 items in your trolley. For the weekly routine that turns this into pounds kept, read five habits that quietly save £20 a week. For how Groceria does the comparison at scale, see how we track prices across UK supermarkets.
Which?, the CMA and Kantar all publish regular UK grocery comparisons. They disagree on weekly winners — promotions move — and agree on the structure: discounters win on own-brand staples; the big four win on range and the occasional hero deal. Your job is not to pick a "cheapest store". It is to pick the cheapest store for each line.
Beat the layout
You do not need discipline of steel — just a routine that makes the tricks irrelevant:
A note on "was / now" tickets
UK advertising rules expect a "was" price to have been a genuine recent selling price, not a fictional high. Enforcement has tightened after years of complaints. Still, a legal "was" can be a bad deal if a rival's everyday price is lower. Check the unit, check a second store, then decide.
The receipt
What to remember, printed the only way we know how:
Sources and further reading
- Price Marking Order 2004 — unit-price display rules for most pre-packed goods in Great Britain.
- Competition and Markets Authority — groceries market updates on price competition between the big four and the discounters.
- Office for National Statistics — consumer price inflation, including food and the effect of pack-size changes.
- Which? supermarket reviews — independent basket comparisons that move week to week with promotions.