Referred study in the article:

Not all price endings are created equal: Price points and asymmetric price rigidity

https://www.sciencedirect.com/science/article/abs/pii/S03043...

• 9-ending prices exhibit an asymmetric rigidity compared to non 9-ending prices.

• Asymmetry is counter-Keynesian: 9-ending prices are more rigid upward than downward.

• Consumers use 9-endings as a signal for low prices, influencing their perceptions.

• Retailers set 9-ending prices more often after price increases than price decreases.

• The findings hold for regular/sale prices and for inflation/no-inflation periods.