Amazon operates a volume-based advertising fee structure. The more products that are shipped as a result of your affiliate links, the more you'll make per sale. Once you have sold enough products to move up to a different advertising rate, all subsequent sales will give you commission at that rate, until and unless you reach the next fee level. Note that some products are exempt from this commission structure.
PA API or Data Feeds may allow you to access data, images, text, and other information and content relating to products offered on one or more affiliate sites. If you use PA API or Data Feeds to access or use any such data, images, text, or other information or content, you agree to comply with and be bound by the terms of the applicable license agreement for PA API or Data Feeds (or equivalent service) providing Product Advertising Content from such affiliate sites.
In February 2000, Amazon announced that it had been granted a patent on components of an affiliate program. The patent application was submitted in June 1997, which predates most affiliate programs, but not PC Flowers & Gifts.com (October 1994), AutoWeb.com (October 1995), Kbkids.com/BrainPlay.com (January 1996), EPage (April 1996), and several others.