This come from a British campaign for KFC (btw, it's amazing how popular KFC is abroad)...
KFC’s $1 fries chips were a great deal. But the promo ran for years and had gone stale. Ogilvy was hired to make the campaign fresh—without changing the product or price. So they tested 90 different ways to say "$1 chips. ”The winner?
A deal so good you can only buy 4.
When you give customers a reference point, it becomes the baseline they compare everything else to. Without it, someone might grab 1… or none. But add "limit 4,” and suddenly 4 becomes the natural benchmark.That’s why sales of chips jumped 56% compared to the previous year. And sales for exactly 4 orders of chips shot up 84%.