The shelf price lies — the unit price does not
Why a bigger pack is not always cheaper, and how to check in ten seconds
The most common comparison in a supermarket is also the most wrong: look at two prices, take the lower one. The trouble is that the shelf price answers a different question from the one you asked.
What a unit price actually is
A price per unit of measure is what a kilogram, a litre or a single unit of the product costs — regardless of the pack size that happens to be in front of you. It is the only number that lets you compare a 100g pack with a 180g pack without fooling yourself.
The maths is simple: price divided by quantity. A 100g pack at ₪5 is ₪50 per kilo. A 180g pack at ₪8 is about ₪44 per kilo — so the pack that looks more expensive is in fact the cheaper one.
The opposite mistake: "bigger is always better value"
Most of us have internalised that a family pack is cheaper per unit, and so we stop checking. That assumption is exactly what makes it possible to sell a large pack at a higher unit price — it looks like a saving, so nobody does the sum.
Sometimes bigger really is cheaper, sometimes it is not, and the difference between the two cases is one calculation. And even when the large pack does win on unit price, it is not automatically the right buy: a product that spoils before you finish it is 100% more expensive, not 10% cheaper.
Where it gets especially slippery
Three cases where the eye fails almost every time. Products sold by weight against products sold by count (nappies, batteries, wipes), where the difference between 40 and 52 units disappears into the packaging design. Concentrated versus regular formulas — laundry detergent, fabric softener — where the real parameter is the number of doses, not the volume. And "2 for" promotions, which only change the unit price if you genuinely take two.
In all three cases the shelf price is perfectly accurate — and does not answer the question.
How to check without doing mental arithmetic
The price table on the site carries a price-per-unit column next to the price itself, so comparing different pack sizes does not require any maths from you. In the shop, Israeli shelf labels are required to show the unit price — it is there, in the corner, in small type.
And if you want to be sure you are comparing the same product at all, the barcode is the way: the same barcode means the exact same pack, which keeps a price comparison between chains honest.