Costco is for bulk staples and commodities for me. Products that I really don't need the best of the best for, good enough is good enough and as long as I can use it all before it goes bad, I'd rather not waste more thought than needed for it. Milk, eggs, flour, flowers, microfiber towels, batteries, salt and pepper.
Then for all the niche stuff that I do truly care about, there's the specialty stores or really the farmer's market. That's where I'll indulge for the first press seasonal olive oils, all sorts of pluot/apriplums/plumpicots combinations, short shelf life wild berries, blueberry/orange/mint blossum honey and whatnot.
> Costco is for bulk staples and commodities for me
> Milk, eggs, flour, flowers, microfiber towels, batteries, salt and pepper
If you can walk out of Costco month after month with just those essentials, and never pick up any of the nice-looking and reasonably-priced goodies there, I think it's safe to say that you have the level of discipline required to be financially successful and not have to care about whether you're getting the best price per unit of whatever it is you're buying. :-)