Costco’s whole thing is selling larger quantities, most times at a lower per unit price than other retailers such as Walmart. Walmart’s wholesale competitor to Costco is Sam’s Club. Also, Costco’s price labels always show the per unit price of the product (as do Walmart’s, in my experience).
Often a false economy. My MIL shops at Sam's Club, and ends up throwing half her food away because she cannot eat it all before it expires. I've told her that those dates often don't mean the food is instantly "bad" the next day but she refuses to touch anything that is "expired."
My wife is the same way - the "best by" date is just a date they put for best "freshness". "Sell by" date is similar. It's not about safety.
My wife grew up in a hot and humid climate where things went bad quickly, so this tendency doesn't come from nowhere. Her whole family now lives in the US midwest, and there are similar arguments between her siblings and their spouses.
The ones I’m talking about were only subtly different, like 22 oz vs 24 oz. To me it was obvious what they were doing, shoppers couldn’t compare same-size units and they could have more freedom with prices.
There is no federal law requiring unit requiring unit pricing, but the the NIST has guidelines that most grocery stores follow voluntarily. 9 states have adopted the guidelines as law.
I don't think that's correct. Prices for retail goods aren't usually even attached to the product in interstate commerce, and are shown locally on store shelving.
