Why 19.99 feels cheaper than 20

The aha, in writing

1. 19.99 is just one cent less than 20, yet it reads like a whole different number.
2. You read numbers left to right and the first digit grabs most of your attention, so 19.99 feels closer to 19 than to 20. Researchers call it left-digit bias.
3. In more than 22 million used-car sales, prices dropped suddenly each time the mileage crossed a 10,000 mark, with smaller drops at every thousand, a pattern traced mainly to final buyers, not professionals.