The single most common Costco mistake — the one that costs members the most money and generates the most food waste — is not buying the wrong product. It is buying the right product in the wrong quantity for the wrong household. A 25-pound bag of jasmine rice is an extraordinary value for a family of four that eats rice four times a week. It is an expensive commitment for a single professional who makes rice occasionally. A 5-pound bag of spring mix is a week's worth of salad