Amazon tests varying free shipping thresholds based on zip codes, leaving some customers 'annoyed'

FILE - Packages pass through a scanner at an Amazon fulfillment center, Aug. 3, 2017, in Baltimore. Amazon has been quietly raising the amount some customers need to spend on its site to get free shipping. To qualify for no-cost deliveries, some Amazon customers who don't have Prime memberships now need to spend $35, up from $25 previously. (AP Photo/Patrick Semansky, File)