When you stroll into Costco, leaning with swagger on your huge cart and confidently flashing your membership card at the entrance, there’s an atmosphere in the air of “I’m going to spend a lot of money today, but things will be so much cheaper than shopping elsewhere.” For some items (huge pack of super-thick steaks, we’re looking at you), that’s true, but no store is the best place to buy everything and some Costco items aren’t always going to save you any money.

Marketwatch has put together a roundup of such non-value Costco purchases, but since it’s a slideshow and everyone hates slideshows, we’ll save you some trouble of having to click-click-click.

Stuff you might want to avoid buying at Costco.

• Books and Other Media
The prices might not be bad at Costco, but the selection is often wanting and you’ll probably do a lot better in terms of both price and suggestion online.

It’s impulse buys like this — you see some bestseller a friend recommended and decide to pick it up — that help Costco make up for the bottom-dollar prices on other things, but it’s not your job to improve a store’s bottom line.

• Oversized Condiments
The Marketplace story flat-out says to not buy condiments because the containers are so large that they will spoil before you use them up.

But large families or people who cook frequently may indeed use these up before they go bad. And as we’ve written numerous times, a sell-by or use-by date on food does not mean it’s actually gone south.

Our rule of thumb would be: If you’re not sure that you’ll use up all that ketchup in the next few months, don’t buy it.

• Diapers
This one surprised me (of course, the closest I’ve come to small children is waving politely at my friends’ babies), but Marketplace claims that Amazon, Target and Walmart have better prices on diapers.

• Paper Items
Another one we weren’t expecting, as one of the stereotypical Costco purchases is the massive car-sized block of toilet paper or paper towels, but Marketplace says you may be able to do better with coupons at the supermarket.

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