If you are a clickbank vendor and your website receives natural traffic from search engines that actually bring you a sale then clickbank will only charge you the $1-$2 processing charge.
This isn't right. Clickbank will take their 7.5% + $1 from all sales which are processed through their order page.
However the customer found your sales page, if Clickbank are retailing the product, they take their cut. I just checked with them.