That’s just a misunderstanding of Costco. Costco is an expensive store with high quality products for high income shoppers... don’t be fooled by the name.
Both Costco and Sam's Club 25 years ago were truly "warehouse" stores. They had no heat. No air conditioning. They weren't brightly lit as they are today. Nowadays, they both have decent-to-above-average well-lit interiors that are designed to be essentially middle-class (in the case of Sam's) to upper middle-class (in the case of Costco) stores that are just "really big".
They were little more than distribution centers with printed price tags on items back in the mid-90s. A lot has changed, about both chains, since then.
In any case the attitude of the NYT was that people with any money would want to lord it over others. Back before the dot com boom that attitude had not migrated out here.