Most of us look directly at the retail price rather than the cost per 100ml or 100g of product. Supermarkets rely on our buying impulses and psychology so we don’t consider the small print under the price displayed. Here’s a great example of how highlighting a price in with colour tricks us into believing it is the better value and then tries to sell you more. However, take a look at these yogurts. The large is 450g for £1.80 but if you bought 3 x 150g pots for 50 pence each you’d be saving 30 pence. In fact, when you buy two large pots only then does it become as cheap as the smaller pots.
There maybe some advantages though. For example, you may want to use only a small serving rather than a whole small pot, not buy three separates or have the convenience of a big pot. Either way, it is something you should be aware of when you’re shopping, particularly on the products you use in quantity. Try some comparisons next time you’re in a supermarket.