Shopping at Costco tends to save consumers money. If it didn't, they wouldn't be willing to pay their membership fees, which are currently $60 for a basic membership and $120 for an executive membership. It's been more than five years since Costco raised its membership fees, so members are actually due for a hike.
You'll often hear that buying groceries at the supermarket is more economical than purchasing prepared meals. Such is the case right now with frozen organic strawberries sold at Costco, Trader Joe's, and Aldi, among other stores. The great thing about shopping at grocery stores that pride themselves on solid customer service is that in situations like this, you don't have to worry about losing money.
My family generally shops at Costco on a weekly basis, and when it's my turn to pick up groceries, I often take a "get in, get out quickly" kind of attitude. It's not that I don't love Costco, but rather, I tend to be pressed for time during the workweek, so I try my best to limit the minutes I spend in the store.