One of last week's biggest gainers is also one of the more surprising winners in recent months. Shares of Blue Apron Holdings (NYSE: APRN) moved 16.1% higher last week, fueled in part by an analyst offering up some encouraging words about its distribution partnership with warehouse club giant Costco (NASDAQ: COST) with another Wall Street pro suggesting that Costco could just outright buy the gourmet meal-kit provider .