Over here it'd be on the seller to facilitate the returning of the package and cover expenses for their mistake and then get it sent off to the rightful buyer.
Like when I've received stuff that wasn't meant for me, they have to make sure that I pay nothing and have little to no hassle returning it. Some even argue that it should be picked up by the company and if you make it clear that they can physically pick it up you're in the clear.
Whether that extends into the world of ebay I don't know
