Have you A/B tested making the buy button more obvious? Bigger and more prominently colored? Also, maybe you're better off, for the cases where you have multiple affiliate links, to make one of them big and shiny and put in small letters below 'also available on...' You'd made the affiliate that pays out most the prominent one of course, if your contract allows that. I like the site, this would be exactly the type of site I'd love to have if I were in the market for an ipad case.