"The customer is always right" is better read as, "Sell the customer what they want to buy (if you can)". That doesn't mean the customer gets to mistreat or as

"The customer is always right" is better read as, "Sell the customer what they want to buy (if you can)". That doesn't mean the customer gets to mistreat or assault your employees over the proximity of pickles to their hamburger patty when it was being cooked, but that if enough customers ask for more meat on their burger then you should offer a double or triple patty option.