Dear Economist: Why does a twinpack cost more than two singles?

Dear Economist,
A single Milky Way costs 20p in my local corner shop. A twin pack costs 47p. I’ve made a habit of checking the prices in other shops and a twin pack invariably costs more than two singles. What could be the cause of this apparent madness? The madness in pricing, that is, not the madness of a twenty-something compulsively checking the price of children’s sweets.
Kendrick Curtis, via e-mail

Dear Kendrick,

I am composing this reply overseas, far from the British corner shops where I can check your story, but what you say rings true. In my own travels around shops with a clipboard – a sure way to make the staff twitchy – I have often discovered products with an unexpected mark-up. One example was the medium-sized pack of washing powder priced at rather more per 100g than the small or the large.

All shops want to offer competitive prices to customers who demand them, while charging more to customers who do not much care. Random mark-ups will do the trick: they are easily avoided by bargain hunters but will often snare the unwary.

You are right that it does feel mad for a twenty-something to check the price of children’s sweets; that is why the pricing you describe is clever. I am confident that many adults do not consider the price of confectionery, and that most children do. If I am right, the mark-up on a twin pack is likely to be aimed with pinpoint accuracy at greedy, careless grownups. The children will find the cheaper deal – if they want two Milky Ways, they can buy two singles. Adults, their wallets overstuffed and the days of saving for penny chews long forgotten, will grab for a twin pack and pay more. It seems to me like sweet justice.

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