I don’t really “get” shopping at Costco. For starters, you have to pay to become a member, which essentially means you need to buy the right to become their customer.
Then when you get there, you feel you have to buy in quantities that rival army rations. And on your way out, they practically frisk you to make sure you’re only carrying what you paid for.
I guess they want to make sure you don’t have 394 pounds of hamburger hidden somewhere.