Costco's reported margins did contract, but that was accounting trickery related to a change in revenue recognition and gas price inflation. Under Armour (NYSE: UA) (NYSE: UAA), Dunkin' Brands (NASDAQ: DNKN), and Costco Wholesale (NASDAQ: COST) hit new highs last week. Costco Costco made the cut in this column a couple of weeks ago, but when an analyst decided to downgrade the warehouse club operator ahead of its quarterly results late last month, it seemed as if the stock would fall out of favor with investors.