The Costco stores near me are a madhouse on Friday evenings and Saturdays. Friday evenings more so in the summer when everybody is buying mass quantities of food for get togethers over the weekend. It is not uncommon on a Saturday afternoon to have 50 to 75 customers in line to check out, but it usually fairly orderly. I went to Costco on Wednesday during my lunch hour. I had to park in the back 40 during the day on a weekday. I suppose a lot of folks were off work this week.
The only reason I have a Costco membership is for my concession stand once a month for the warmer half of the year. My membership expires today and I don't plan to renew until April or May to save a few bucks. I would save enough for myself to justify a membership, but I save plenty on stuff for my concession stand.