[wesleyd]

I don’t even think Costco is all that cheap!

Yes, many things are slightly - a few percent - cheaper than many other stores, per unit weight/volume, but it’s not a a big difference. Some things are more expensive though, like meat and fish. It seems “cheap” only if you do most of your other grocery shopping in premium grocery stores (eg Whole Foods). I do most of my grocery shopping in Market Basket, and it’s about the same as Costco for most things I buy. And everything comes in normal sized portions!

Costco’s real benefit is that everything they sell is pretty good stuff, and nothing is outrageously overpriced. Eg They sell Goya beans, for more per can than supermarket brand beans, but less than Goya beans in supermarkets. Many things are like this. You can assume that the things Costco sells are The Good Brands, but you can get most things cheaper if you’re not brand sensitive.

There are many things for which buying in bulk is a false economy: I will *ever again buy Costco-sized containers of eg yogurt covered raisins, or praline covered almonds! I suspect that every trip to Costco used to raise my average body weight for the next year by half a pound. Especially if I went to Costco hungry! Never go to Costco hungry!