[1]: They sell the things at a profit, then turn that profit into more infrastructure to sell things before it gets to the shareholders -- which may or may not be the best deal for the shareholders, but that part impacts the customers little.
[2]: "many products" - what, Prime and the Kindle? Plenty of people don't interact with either. :P
Their financial reports sure don't support that theory. Apart from making very little profit as a company [1], they sell many products at a loss [2].
[1] http://www.engadget.com/2013/01/29/amazon-calendar-q4-2012-e...
[2] http://www.newstatesman.com/blogs/technology/2012/10/amazon-...