JCPenney tried changing all their prices ending with .99 to the round dollar amount. It was catastrophic for their sales, so they changed it back. It was a part of a larger plan by Ron Johnson (former senior VP of retail at Apple) to get rid of the "pricing game" of stores and to stop deceiving customers with fake sales/markdowns and deceptive pricing. It caused JCPenney's stock to halve and then some, and got him fired within 15 months. Here's an ad they showed that apologized to customers for using accurate & honest pricing instead of deceiving them, and begging them to come back
The power of the number "9" isn't confined to the cents column, either. One American clothing retailer experimented by changing the price of a dress from $34 to $39 dollars and increased sales by over 30%.
Consumers are fucking idiots. Humans are stupid dumb animals that like patterns too much for their own good and short circut their brain immediately after seeing minimal information to fill in the blanks. If you like patterns so much, why don't you marry them? Hmmm???
Pfft, silly object-oriented devs. My children are named Typeclass and Iterator! Scala Design Patterns prove themselves to reign supreme once again. Enjoy sending your kids to public coding bootcamp.
This is also why gas pumps measure gasoline to the thousandth of a gallon. Consumers LOVE to see those numbers racing upwards and think, "Whoaaaaa! Look at those numbers GO! I must be getting an awesome deal!"
It's a deliberate psychological trick, played on you by energy companies to fool you into thinking you're getting more than you really are.