Re: Costco and/or Sam's Club
I belong to BJ's (nearest Sam's is across the river) and find that things like coffee, bottled water (don't forget to recycle!), some pastas, soups, butter and chicken are a definite savings... just the two of us so we go once a month and I freeze a lot of stuff. Also some cheeses, and household goodies, detergent and batteries.
Name brands are usually just about the same or a little less (or more!) than the regular retail stores, unless they get a batch with a box misprint.
Many things like frozen veggies only come in grmongous packs and so it's not worth it to buy them, but there are sufficient savings that the membership fee is well covered and if you DO need a big-ticket item, (last year I bought an 8-man tent for a ridiculously low price), often the savings will take care of several years of memberships right then. At $40 a year for both of us, I figure I'm covered until 2050 or so.