The cheapest grocery store in the country is Walmart ... among the 20% cheapest of all store-brand products. Aldi, the discount supermarket chain, was the second-least expensive of the five ...
But, Costco is of course, a buy in bulk store, so that's a little different. Those prices are a bit more because of the bulk. I have friends that love to buy in bulk at Costco or BJ's, I don't usually ...