+ - https://docs.aws.amazon.com/AWSECommerceService/latest/DG/EX_RetrievingPriceInformation.html
+ - https://docs.aws.amazon.com/AWSECommerceService/latest/DG/ReturningPrices.html
+ - https://developer.amazonservices.com/
+- monitor Amazon order status
+ - https://developer.amazonservices.com/gp/mws/api.html?group=orders§ion=orders
+- monitor eBay order status
+ - http://developer.ebay.com/DevZone/XML/docs/Reference/eBay/GetOrders.html