Costco has been one of the most successful retailers in recent years, weathering the economic downtown and emerging as a strong competitor in the discount retail space. Costco's secret to success is its focus on offering high-quality merchandise at low prices, which has resonated with consumers and investors alike. It has performed well this year, posting strong sales and earnings growth. However, there is a danger that the stock is now overvalued. Costco trades at a significant premium to its peers and its own history.