There is no fee to list a product on RD2RD. There is a service (transaction) fee when products are sold. Service (transaction) fees are charged to offset costs associated with hosting of content, website security, payment processing, website development, marketing, etc.
Basic members earn 65% of each sale, and premium members earn 80%. The remainder is a service fee that is paid to RD2RD. Click here for more about premium membership.