Fastbay offers a wide range of customization possibilities related to sending the shipping costs of your products to eBay.

The standard configuration provides that the costs are calculated dynamically based on the carrier / Prestashop areas mapped towards the eBay carriers.
as described in the Shipping section of the documentation.

If you need to differentiate shipping costs by eBay category, you can do so by activating the Business Rules support.

This will allow you to create ad hoc shipping rules in the module and associate them in Fastbay. Following the association the module
will ignore the standard configuration and apply the associated rules.

It is also possible to customize the national shipping costs for each product, through the dedicated Fastbay editor within each product.
product card Prestashop. This functionality is described in this section of the documentation.