This is not surprising. Look at Google search results. The ads are first 4 rows. You can raise the bid but win 2nd spot instead of 1st and still not get the click. At the same time 2nd spot will get more attention than 3rd spot. So more clicks.MalcolmJWardlaw said:What perplexes me is that the CTR also goes up at the higher flat-rate bid (it roughly doubled). I would expect CTR to be purely a function of the inherent attractions of the book cover.
As an advertiser the closer to the first you are the better your CTRs will be purely because some people only click the first result and nothing else. Amazon ads is a similar system so no surprise the better your bid the more clicks you get.