Money & WorkFact
Why almost nothing costs €10 but everything costs €9.99.
Reading left to right, the first digit anchors most strongly. €9.99 gets stored by your brain as nine-something rather than ten, even though the difference is one cent. Studies show prices just below a round number measurably sell more than the round number itself. The trick is over 100 years old and still works.
Useful: Round up consistently in your head: €9.99 is €10, €199 is €200.
Source: en.wikipedia.org