Costco runs an incredible business, but its valuation has become expensive. Costco Wholesale (COST 0.35%) has been a reliable market-beating stock for ages. The company operates under a warehouse model that breeds loyalty and sales growth, and it also pays a dividend. There's nothing not to like about Costco stock -- except for its valuation. Is Costco's premium valuation a setup for a fall? Why Costco stock keeps climbing Costco has 879 warehouse stores globally, 606 of them in the U.S. It stands out from ...