I have been seeing a number of claims that the full quote ends with “…in matters of taste.” As much as I would love that to be true given that retailers have been bludgeoned with the phrase over the years, it apparently is not. While Harry Selfridge is credited with creating The Customer is always right, there is no record of him completing it with a sentiment about taste.
Reinforces the idea that you always need to research such things before taking them at face value. Which is apt because according to wikipedia, the saying was used to create a sense of confidence in people at a time when caveat emptor, let the buyer beware, was the maxim of the day because malpresentation was so rampant.
While the phrase is attributed to various people, the intent was to assure customers in the early 1900s that the merchant would work to guarantee their satisfaction.
About 10-15 years later, various people were already observing that customers were taking advantage of the saying to bully merchants and engaging in a little misrepresentation of their own. So it has continued for over a century as witnessed by the fact that people are trying to append a few more words to the saying to create a counternarrative.
Certainly, more than a century later there is also plenty of misrepresentation coming at us through various media to warrant the use of caveat emptor as well.
Perhaps it is time for a new saying that both tempers customer demands and urges a degree of discernment before purchasing.