Cost per click was more common in the early days of affiliate marketing but has diminished in use over time due to click fraud issues very similar to the click fraud issues modern search engines are facing today. Contextual advertising programs are not considered in the statistic pertaining to the diminished use of cost per click, as it is uncertain if contextual advertising can be considered affiliate marketing.
I concluded that having read a product review, people felt more informed to make a purchasing decision. As a result, if they did click a link after reading the review they were more likely to buy the product. Those clicking on the top link seemed to be more in a ‘surfing’ mode. They clicked on the link less because they wanted to buy it but more out of interest to learn more. Some bought the product and some bought other products once they were ‘in the door’ at Amazon.