At a guess, Amazon is counting all traffic that follows your links, including spiders/bots... and analytics only counts people with javascript enabled. So the true number of humans probably lies somewhere in between Quantcast analytics gives you a good breakdown that includes real visits/uniques plus their estimate of how many sets of real human eyeballs see your page... adding that for a month or two might give you a better idea of your position. And btw, imho more or less traffic numbers is of very little importance when it comes to converting. Focussing on attracting the right traffic, then speaking to it smartly, will result in more sales. Don't look at the numbers, just think about what someone who is ready to buy that prouct will be thinking about and where they will try and find it first. 1 good link on a relevant page that sends 10 clicks a month can be the basis of a reliable income stream. You don't even need to work hard if you work smart enough.
It's normal for a side bar link on something that doesn't really relate to your content (Amazon products for people who come looking to play poker) to have a terrible conversion rate, like below 0.5% It's not normal for targeted content specific to the searches people are following to get to your content to have such a bad conversion rate. So far this month I have a 10% conversion rate for Amazon from a blog which does book reviews.