Vì sao giá rất nhiều món hàng kết thúc bằng 99 xu?

các nhà bán lẻ định giá theo thói quen (chứ ko tối ưu hóa theo nhu cầu), nghĩ rằng người mua hàng đọc giá bỏ 2 chữ số thập phân, 

nhưng theo tính toán, làm vậy mất khoảng 1 đến 4% lợi nhuận gộp...

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Firms arguably price at 99-ending prices because of left-digit bias—the tendency of consumers to perceive a $4.99 as much lower than a $5.00. Analysis of retail scanner data on 3500 products sold by 25 US chains provides robust support for this explanation. I structurally estimate the magnitude of left-digit bias and find that consumers respond to a 1-cent increase from a 99-ending price as if it were more than a 20-cent increase. Next, I solve a portable model of optimal pricing given left-digit biased demand. I use this model and other pricing procedures to estimate the level of left-digit bias retailers perceive when making their pricing decisions. While all retailers respond to left-digit bias by using 99-ending prices, their behavior is consistently at odds with the demand they face. Firms price as if the bias were much smaller than it is, and their pricing is more consistent with heuristics and rule-of-thumb than with optimization given the structure of demand. I calculate that retailers forgo 1 to 4 percent of potential gross profits due to this coarse response to left-digit bias.

That is from a forthcoming paper by Avner Strulov-Shlain.