It doesn't have to do with Amazon. It is just how ads work. Of course when you buy a product that is heavily advertised you know that you are paying for it, Amazon or not. That's why, when I see an ad campaign for a product I may want, it is a signal for me to look elsewhere. Some competitor may use what would be ad budget towards offering lower prices or better quality. As for Amazon, it is not cheap! It is convenie…
It has everything to do with amazon.
Amazon has chosen to embed ads into the navigation used to shop on their site. It is a conflict with the customer's needs in just about every way possible.
I think the only time I saw something so blatant was years ago at the Cheesecake factory, where they had ads in their menu (not really food-related)