Rice
In most cases, except when I have my family from Florida over, I prefer to buy rice in small packages from ethnic supermarkets. Once, when I needed a bigger quantity, I went to my local neighborhood market and found a 25-pound bag of rice for less than $15 compared to Costco, where I would have paid $40 for a bag of the same size. Rice and other whole grains contain oil that adheres to the grain and may hasten rancidity, in addition to the price difference.
Have you ever bought rice from Costco? Were you satisfied with it? Tell us in the comments.