We do a variety of retargeting on behalf of sellers.
You however are also encouraged to do your own retargeting on Facebook or Google.
Currently the remarketing we provide on behalf of sellers is free, we do not charge. However in the future, once we are no longer in beta, we will need to account for remarketing costs. These are no effort sales we bring to your products, so the base price for remarketing sales will need to be increased. We will make announcement, when we make this change.