Costco’s (COST) same-store sales rose 9% the last five weeks of the year. Net sales rose 14% for the period to $7.24 billion. Analysts had expected less.

Before Wall St. bids the stock up, it should answer the question about what the revenue cost Costco.

Circuit City (CC) was hammered when it announced a loss due to deep discounts. Costco may have had to cut margins to keep up with retailers like Wal-Mart (WMT).

Costco’s last quarter was strong, but it trimmed the high end of its forecasts. Investors should hope it does not have to cut again. Costco’s stock is up only 5% over the last year, so Wall St. is already skeptical.

Douglas A. McIntyre can be reached at douglasamcintrye@247wallst.com. He does not own securities in companies that he writes about.