No doubt variance swamps our puny personal experiences, but for the little that it's worth I've had the opposite: instant return at Costco no questions asked, and a half hour lineup to return a wrong product I'd just mistakenly bought at Walmart. To be fair to Walmart, though, it wasn't their cashiers' fault. There were only two customers in front of me and both were so obstreperously difficult that it became an amusement to watch what ridiculous thing would happen next. One was returning a shopping cart full of dozens of items of clothing. The other was returning a single can of soup. Soup guy was the harder of the two.