Further, Costco's leadership in Wholesale is arguably one of the best reasons Costco may be immune to Amazon-like disruption. Differentiating itself from average grocers by selling large-ticket items and groceries in bulk, Costco's average customer purchase is much heavier and larger than purchases from Amazon or Walmart. If expedited shipping does catch on in wholesale, distribution centers will need to be close to customers in order to minimize shipping costs. Fortunately, Costco already has 748 warehouses at an average size of 144,500 square feet each.