shares of costco wholesale corp cost dropped nearly 1 in the extended session thursday after the retailer reported june sales of 2286 billion an increase of 04 from the 2278 billion in june 2022 comparablestore sales fell 14 including a drop of 25 for us samestore sales ecommerce sales fell 07 costco said costco stock ended the regular trading day down 07 the retailer last month reported a 12 rise in may sales