Goblin barges carry second hand goods from Auradon to Goblin Wharf. The things that the goblins bring tend to be junk like clothes people in Auradon no longer want or lipstick which is no longer in style. The things that are brought by the goblins are partially why the Isle of the Lost is also called the Isle of the Leftovers.
Return to the Isle of the Lost
When the group make it back to the Isle of the Lost they see goblins in the streets living in cardboard boxes and warming themselves near trash can fires. The first thought was that they were goblins from The Isle of the Forbidden who had come over but soon learn that they had been the enterprising goblins who once ran the barges. The reason they were on the streets was that the goblins had supported Maleficent because she promised them freedom. However when Maleficent was turned into a newt, as consequence for conspiring against Auradon an embargo was placed limiting the number of barges that could carry goods putting many goblins out of work.