With low prices on bulk-sized items, Costco has attracted thousands of loyal customers willing to spend at least $60 per year for its membership fee.

The wholesaler is ranked No. 2 for best reputation in a recent Axios Harris Poll and its global membership renewal rate is a steady 90.5%, according to Costco's most recent earnings report. 

However, while its prices are typically low — especially for its Kirkland Signature store brand — not everything at Costco will be sold at the lowest prices you can find. Costco also doesn't price match with competitors.

And with bulk sizes, you can have too much of a good thing, particularly food that's going to spoil within weeks of being purchased.

To help navigate the aisles, CNBC Make It asked Julie Ramhold, a consumer analyst at DealNews.com, for some of the best Costco deals, as well as other items worth skipping.

What's worth buying

1. Gas

Costco consistently has lower gas prices when compared with local gas stations, although you'll need a $60 Costco membership to access their pumps. As of Thursday, a regular gallon of gas at a New York Costco runs $3.39, according to GasBuddy data. At many competing gas stations nearby, a gallon costs about $3.70.

The only catch with Costco gas is that "everybody in town knows it's cheap," says Ramhold. That means that lines are common, especially on weekends or just before and after work hours during weekdays.

"If you have the time and you need gas, by all means, get gas while you're there, because it's well worth it," she says.

2. Nuts

Costco has a wide variety of nuts that come with some of the lowest prices you can find.

"I've never seen another store beat Costco prices, whether you're buying cans of salted peanuts, mixed nuts or if you're buying three pounds of raw almonds," says Ramhold.

But since Costco sells nuts in bulk, make sure you aren't buying more than you normally consume, as they can spoil over time. Whole nuts last up to a year when stored in a freezer, but unshelled or ground nuts only last about six months, according to Food & Wine.

3. Maple syrup

A 33.8 ounce jug of Kirkland-branded maple syrup can be found for $14.99, which is at least a few dollars less than what you find in regular grocery stores, or even in big box stores like Walmart.

"When you break down the unit price, it's much better compared to shopping at regular grocery stores, or even big box stores like Walmart," says Ramhold.

Kirkland brand maple syrup is a hit with Costco-focused food review websites, with one rating it a "must buy."

"It's so good," says Ramhold, who uses it as a sweetener in a lot of her baking. "It's something that's always in my fridge." 

4. Eggs

Even when egg prices shot up by 82% in 2023, Costco had some of the lowest prices on eggs you could find in stores, says Ramhold.

Costco offers a wide variety of grade A-certified eggs, including organic and cage-free brands.

And Kirkland Signature eggs hold up well when compared with grocery store house brands. With some store brands, "the egg shell will be weirdly thin," says Ramhold. "With Costco, their eggs are always perfectly fine."

5. Pizza

Costco's famously cheap $1.50 hot dog and drink combo gets a lot of attention, but you could argue the store's food court pizza offers even more value.

At $9.95 for a large pizza, "you can easily feed a family of four," says Ramhold. The cost of Costco pie is nearly half the national average, which is $17.81, according to a recent report by Slice, a technology platform for pizzerias owners.

Individual slices are cheap at only $1.99.

What you can skip

1. Spices

Costco's spices are competitively priced, but they're also sold in bulk quantities that can be impractical for an average household.

That's because ground spices have a limited shelf life of about six months, after which they lose their potency. In that case, you probably don't need to buy Costco's five-pound tub of turmeric, even if it's at a great price. With spices, you'll want to only buy what you actually need. 

"For a giant container of chili seasoning, if you're not planning on making chili every single weekend, you probably don't want to get something that big from Costco," says Ramhold.

2. Fresh produce

As with spices, fresh produce is sold in bulk sizes that are typically larger than what you find in regular grocery stories. 

But unless you have a few meals planned out for a six-count bag of cucumbers or a 20-lb bag of potatoes, you're likely to waste some of that food. That could negate whatever cost savings you'd get from buying in bulk, Ramhold says.

3. Apparel

Costco has competitive prices on apparel, especially for its Kirkland Signature brand. However, compared with other big box stores like Walmart or Target, the selection is limited, especially in stores. There's also no fitting rooms in which to try clothes on.

"I wouldn't spend a lot of time browsing Costco's clothing, because it's probably going to end up being a waste of your time," says Ramhold. 

4. Books

Book prices at Costco aren't cheaper than what you might find at a place like Amazon. The selection isn't very good, either, unless you're looking for bestsellers or kids' books.

Plus, you can often find these books for much less secondhand, if not for free at your local library. 

"If you're looking for something aside from bestsellers, you may have trouble finding it," says Ramhold. "I pretty much just ignore that section."

5. Dairy products

Costco has great prices on dairy products, but they're sold in bulk sizes that can spoil before they are consumed.

Stay away from softer cheeses and yogurts as they tend to expire the fastest, usually within a few weeks.

"Three pounds of cottage cheese for seven bucks is a great deal," says Ramhold. "But you're not going to eat it fast enough to make it worth it."

While hard cheeses will last longer, you still need to be realistic about portion sizes. Considering that Americans only eat an average of about 3.3 pounds of cheese per month, Costco's five-pound packages of cheddar might be more than you need.

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