Seemingly every time Amazon.com (NASDAQ: AMZN) makes a move in the grocery space, Costco (NASDAQ: COST) stock falls.
That happened again recently, when the online retailer announced that its deal to purchase Whole Foods would close on Aug. 28 and that some prices would be lowered immediately. That news sent Costco shares from $159.37 at market close on Aug. 23 to $152.45 at the close of trading Friday, Aug. 25, a 4% drop.