Worst: Sunscreen
You should know that sunscreen is only effective for up to 3 years. If you get a Costco multipack, make sure to check its expiration date to see if it will still work for you. No one likes to waste money, after all.
Worst: Disposable Razors
Even though it might sound like you are getting a good deal when you buy a huge box of disposable razors, you should go to Walmart instead of Costco. The latter offers 14 Kirkland razors for $23, which means each razor costs $1.64. Meanwhile, you can get 10 Gillette disposable razors for $7.97 or $0.80 a piece at Walmart. We will let you do the math!