I like Hunter Walk's notes on this article.

I’ve always been fascinated by the science of sales, especially in a retail setting. “Why We Buy” by Paco Underhill is one of my favorite quick reads on the subject. You’ll never look at a store the same way again!

The Atlantic did a round-up of research into how retailers try to part us from our money. Here are some of my favorite findings:

• “we perceive prices to be lower when they have fewer syllables and end with a 9”
• “one recent study found that, compared with friendly salespeople, rude clerks caused customers with low self-confidence to spend more and, in the short term, to feel more positively toward an ‘aspirational brand'”
• “when a customer who feels badly about her appearance tries something on and spots an attractive fellow shopper wearing the same item, she is less likely to buy it”
• “One paper now under peer review shows that cooler temperatures indoors lead to a more emotional style of decision making, while warmth contributes to a more analytical approach”
• “One study found that popular music leads to impulsive decisions, while lesser-known background music leads to focused shoppers”

Source:

https://hunterwalk.com/2016/12/13/why-you-bought-that-ugly-sweater-how-stores-trick-you/