There are many other costs involved in shipping a product in addition to postage. Are you monitoring your delivery area surcharge (DAS) or extended delivery area surcharge (EDAS)? Most carriers have these charges.
Two months ago, Amazon.com Inc. halted orders from thousands of suppliers with no explanation. Panic ensued — until the orders quietly resumed weeks later, with Amazon suggesting the pause was part of a campaign to weed out counterfeit products. Suppliers breathed a sigh of relief.