Very few companies have a true moat around there business. In most cases, a rival can find a way to beat its prices, match any services it offers, and compete in unexpected ways. Costco  (COST)  does not have a unique business as Sam's Club and BJ's Wholesale operate under the same model, but it does have a moat. Once members are in, they're very likely to stay members and, if there's some sort of drop in renewals, the chain usually sees that a year out, giving it time to adjust its strategies. It's not ...