Cheese, pasta, broccoli, nuts, and a number of other things are cheaper at Costco, and of good quality. You also have to compare like quality or desired attributes, not just price, e.g. are the eggs organic or free-range? Are the nuts from China, grown in soil full of heavy metals, or are they from California? How does the pasta cook up? The Wellcome pasta I’ve had sucked, in comparison. Costco has unsalted nuts, for those who prefer to roast and salt their own, or have them unsalted. OTOH, the choc chips at both supermarkets and Costco are the typical low-end (but name brand), sugar-laden junk.
If you’re interested in a particular item, ask, but nobody’s likely to do a comprehensive assessment for you.