Why does a ₩9,900 price tag look cheap?

When we look at a price, we grab the leftmost number first. ₩9,900 starts with 9, while ₩10,000 starts with 1 and has one more digit. Though the gap is only ₩100, the mind files them into different boxes: the nine-thousands and the ten-thousands.

In 2005 experiments, U.S. researchers Thomas and Morwitz showed that people judge price pairs as more different when the first digit changes, even when the gap is the same. Even if you read every digit, the first impression is set by the leading one.

The effect shows up in real sales, too. When U.S. researchers Anderson and Simester tested a women's clothing mail-order catalog, the same item sold more at $39 than at $34. The price went up, and sales went up with it.

One explanation is that an ending of 9 reads like a signal of a discounted price. Fine-dining menus, by contrast, often show round numbers without those endings. They'd rather stress quality than look cheap.

It's easy to treat a 9 ending as chance, but most are chosen on purpose. Even small prices, like a ₩1,900 drink or ₩990 snack at a convenience store, often end in 9.

On one item, ₩100 is small. But five such items make ₩500, and while each seems to stay under ₩10,000, the receipt total has often already passed it.

When you check a price tag, round the first digit up: read ₩9,900 as ₩10,000 and ₩19,800 as ₩20,000. The cheap feeling lifts and the money you'll spend gets clearer.

The same goes for online shopping. Add a ₩3,000 delivery fee to a ₩29,900 item and you're already past ₩30,000. Adding up in round numbers before you put things in the cart helps you step back from the illusion the 9 creates.