I wouldn't call it a gimmick when the business has been so successful for so many years. They target educated shoppers who want to buy quality at minimum markup and not think too hard about it. If I want a TV, I know Costco will have good ones at a good price. If I need socks, same. Their food is cheaper and better than Kroger. It's just a win-win for shoppers and Costco. The only tradeoff is selection and dealing with the crowds.
What you wrote sounds intelligent but belies an ignorance of the business model.
What you wrote sounds intelligent but belies an ignorance of the business model.