The additional cost field is for other product-related costs (i.e. inbound shipping fee) when configuring the Min & Max price and Your Price.

Users can apply the Additional Cost to multiple listings at once by using a Bulk Action. The added additional cost can be found in the profit calculator of the selected listing(s).

• To set up the Cost for multiple listings, please select the listings you want to set the additional cost to. Following that, visit the “Manage Listings” page and then click on “Bulk Actions”, followed by “Set Cost & VAT”.

• In the pop-up screen, locate the “Set Additional Cost base on ___.” 
• Toggle the On/Off button to turn on or off the setting.