Costco shoppers say these items basically make a membership pay for itself. We did the math.

A 38-pound bag of Blue Buffalo dog food sells for $65 at Costco, while the equivalent weight at a typical retailer would cost $111. At that rate, the membership fee would be offset in less than two purchases.

Assuming 10 purchases a year, this item yields a payback score of 713, meaning the savings would cover the membership fee plus six times the cost of this item alone.

Costco also sells highly rated dog food under its Kirkland Signature brand for $35 per 40-pound bag.

A jumbo pack of Huggies diapers sells for $50 at Costco, while it would cost about $70 to get the same quantity (156 diapers) elsewhere. At that rate, savings on diapers alone would offset the membership fee in less than four purchases.

Assuming one purchase a month yields a payback score of 373, meaning the savings would pay for the membership fee plus three times again for this item alone.

Costco also sells diapers under its Kirkland Signature brand for a lower unit cost.

Costco sells large containers of Similac for $55, which is about $13 less than it would cost to get the same product at a typical retailer.

That means a membership fee would be offset after five purchases. Assuming one purchase a month yields a payback score of 240.

Costco also sells generic baby formula at roughly half the unit cost of Similac, and Costco's offering is produced by the same leading supplier, Perrigo, that other major retailers use for their store brands.

Costco sells 2-pound bags of Starbucks Pike Place roast coffee beans for $8.40 per pound, while typical retailers sell the same beans for about $12 per pound.

At that rate, the savings would offset the membership fee after nine purchases, or 18 pounds of coffee. Assuming a household consumes 30 pounds of coffee a year — maybe they're journalists? — yields a payback score of 166.

Beyond Starbucks, Costco regularly features local coffee roasters and specially sourced beans from coffee-growing regions around the world at a lower cost than conventional retail.

Costco has 2.5-pound blocks of Tillamook cheddar cheese for sale at $4 per pound, which is about $2.60 less per pound than typical retailers.

Assuming a household uses about half a pound a week would amount to roughly 25 pounds a year.

At these rates, a Costco membership would be almost equally offset by savings on cheese for a payback score of 102.

Bacon is incredibly subjective. Still, the closest match found to this $4.33 per pound thick-cut bacon from Costco costs $8 per pound at a Midwestern grocery chain.

At three pounds per package, that works out to a difference of $11, which would offset the membership fee after about six purchases.

Assuming a household consumes 15 pounds of bacon a year would only account for five purchases for a payback score of 85.

Costco sells chicken stock in packs of six quarts for $9 per pack — that's about a third of what it would cost to get the same amount of chicken stock in individual packs from a traditional retailer.

Assuming three purchases a year (18 quarts total) gives a payback score of 83.

Buying three pounds of Fage Total 2% Greek Yogurt at a conventional retailer would cost about $2.70 more than getting a tub from Costco.

Assuming a household consumes about a pound of yogurt a week on average works out to 17 purchases a year, for a payback score of 71.

One product Costco is known for is its comically large packs of paper products, like these 30-packs of Charmin toilet paper.

Before discounts, the $33 pack works out to $1.10 per roll, which is 37 cents cheaper per roll than an equivalent pack bought elsewhere for $44.

Assuming a household uses 10 rolls of toilet paper a month would mean four purchases a year, resulting in a payback score of 67.

At $1.25 per pound, Costco's six-pack of Barilla pasta costs about $4 less than the same amount bought elsewhere.

Assuming a weekly spaghetti night that uses one pound of pasta, this works out to nine purchases a year, resulting in a payback score of 54.

Costco sometimes sells products in quantities that exceed a year's supply. Brita recommends changing its filters every two months, so this ten-pack would last well into next year.

Still, Costco's pre-discount unit price of $4.50 is about $3 less than individual filters cost at conventional retailers. If purchased in equal quantities, the Costco pack would be about $30 less, for a payback score of 45.

Cascade dishwasher pods cost about $7.30 less at Costco (before discounts) than an equivalent quantity bought at a typical retailer.

If a household runs the dishwasher once a day, it would need to buy four packs in a year, which works out to a payback score of 45.

Bear with us for this one. HVAC filters may seem boring, but manufacturers recommend replacing them at least every three months for optimal performance, and that can add up quickly.

Costco's four-pack of 3M Filtrete air filters comes in at $28 less than the same product elsewhere. Most households will only need to buy one pack a year, though, so the payback score would be 43.

It's also worth noting that there are less expensive types of HVAC filters on the market that Costco doesn't sell. The way Costco executives have described it, the company isn't looking to sell the cheapest available products; it wants to find the sweet spot that balances both high quality and low price.

Opti-Free contact lens solution is about 25% less expensive by volume when purchased at Costco, compared with a traditional retailer.

A household that uses about 12 ounces a month would need to buy four of these packs in the course of a year, with a payback score of 42.

Shoppers can generally save money by switching from national brand medications to generics.

A bottle of 365 tablets of cetirizine, better known as Zyrtec, costs $13.50 before discounts at Costco, while the same quantity from some other stores' brands can easily cost nearly $40.

Still, 365 tablets are more than many households might need in a year, so a single purchase would make sense, resulting in a payback score of 40.

Like medicines and meats, Costco also has low prices on cooking oils. This store-branded olive oil is about half the price per liter of a similar store-branded alternative at another retailer.

Assuming a household uses three liters a year, yields a payback score of 25.

This Arm & Hammer laundry detergent from Costco costs $14.89, or about $0.07 a load, versus $0.11 a load for the same product at other retailers.

Assuming a household would go through two 200-ounce jugs in a year gives a payback score of 22.

Like medications, generic vitamins from Costco can be extremely cost-effective — about 20% less than a similar product elsewhere.

Two adults taking one daily multivitamin each would mean five purchases of these gummies in a year for a payback score of 18.

Costco's $1.50 hot dog and soda combo gets a lot of attention. After all, it's not every day that an executive is explicitly warned to never raise the price.

However, we crunched the numbers, and it turns out that roughly one Costco combo a month (14.4 a year, to be exact) would save you $65 compared to getting a similar meal from a chain like Portillo's or Nathan's.

The bigger advantage is the jumbo pizzas for less than $10. By comparison, the largest pizza Domino's makes is 14 inches, which costs $15 and is actually about two-thirds the area of Costco's 18-inch.

For the equivalent square inches of cheese or pepperoni pizza, Costco's offering is about $12 less, which means the annual fee would be offset with six pizzas.

The math on the $5 rotisserie chickens is slightly less favorable to Costco, as many grocery stores offer a similar product.

What are your best-value buys? Let us know!

We'd love to hear about your best Costco picks. Get in touch with this reporter at dreuter@businessinsider.com and tell us more.