I purchased two items from Amazon in the same order: A gadget powered by a 12v car power socket, and a mains-to-12v power adaptor that was purchased specifically to power that gadget from the mains. The gadget has a design defect so I'm going to return both these items.
Amazon will let me return the gadget free of charge. However, Amazon are going to charge me return postage for returning the power adaptor. This is because the power adaptor is "no longer required", not actually faulty itself.
Are Amazon allowed to charge for returning the power adaptor, given that the thing it was to power is faulty?