Why the useless third option makes you spend more

Imagine a cinema selling popcorn: a small for $3 and a large for $7. Faced with just those two, most people grab the small. Now the seller adds a medium for $6.50 — barely cheaper than the large. Suddenly the large looks like a steal, and sales of it jump. Nobody actually wants the medium. Its only job is to make the large look better. This is the decoy effect, one of the sneakiest levers in persuasion and pricing.

The decoy works because humans are terrible at judging value in a vacuum — we judge things by comparison. Two options can feel hard to rank (cheap-and-small vs. pricey-and-big). But drop in a third option that is clearly worse than one of them, and your brain latches onto that easy comparison. The decoy is 'asymmetrically dominated': it loses to the target on every front, so the target shines by contrast.

You've seen this everywhere — subscription tiers with a suspiciously unattractive middle plan, restaurant wine lists, phone storage upgrades. The decoy is rarely meant to sell; it's meant to steer. Once you know the trick, you can ask the sharper question: not 'which of these is best?' but 'which of these do I actually need?'