That is only part of Amazon's advertising business. If you read their 10-k:
"Vendor Agreements
We have agreements with our vendors to receive funds for advertising services, cooperative marketing efforts, promotions, and volume rebates. We
generally consider amounts received from vendors to be a reduction of the prices we pay for their goods, including property and equipment, or services, and
therefore record those amounts as a reduction of the cost of inventory, cost of services, or cost of property and equipment"
"Vendor Agreements We have agreements with our vendors to receive funds for advertising services, cooperative marketing efforts, promotions, and volume rebates. We generally consider amounts received from vendors to be a reduction of the prices we pay for their goods, including property and equipment, or services, and therefore record those amounts as a reduction of the cost of inventory, cost of services, or cost of property and equipment"
http://phx.corporate-ir.net/phoenix.zhtml?c=97664&p=irol-sec...