I know that this is a controversial stance, but as a single gal, I'm kind of anti-big box stores. I like to buy produce, spices, and even most other goods in small amounts. It is fresher, and I tend to get sick of something--or sick at the thought of eating--something in a can or box the size of a Volkswagen.
I also like lots of variety, and these stores tend to be pretty limited. I guess I tend to like specialty stores as well, rather than overwhelming warehouses. And I feel I find just as good deals at Wegmans.
Plus, of my friends who are fans, I notice a suspicious amount of piles of boxes of cookies, crackers, and so forth with only one or two missing in their crowded garages. So I'm not even sure if they are that much of a savings for people with big families.
I know Costo is a pretty decent company with ethical practices, but for buying in bulk and paying a fee to shop at big box stores--no way.