Thank you for the comment. It is really free , I do not sell user search data I do not even record them, I only use Yandex Metrica to see how users use the site to improve site usability. One main problem is user try to chose "Most reviews" sort option without choosing any Amazon Department (When All Departments is active most of sort options will not work so I do not show them) and I even placed a site tour to make users notice it and it worked for some some users but not all of them but it is an improvement. Actually money comes from Amazon Associates Program that's the only way to monetize the site.