Buy- Plastic Wrap
You should certainly use your Costco privileges to buy Kirkland and Vitawrap plastic brands and products. These products you can keep for years and in large amounts too. These products are every day and can be used across the board, and they are the cheapest at Costco.
Don’t Buy- Shampoo Or Soap
Just like soda, the frequency of soaps and shampoos being on sale is evident. So we would not worry about buying these items at Costco as the bargain and pricing are pretty much the same no matter where or what the store.