Amazon is an enormous retailing multinational which craps over workers' rights and much worse. Given that you are buying from them in the first place, the least you can do is reduce their profit margin by even the small amount you can when you get the chance. It's about all the space for 'resistance' that is offered to us sometimes. As User says, if this troubles your conscience, you can take the legal option of asking if they wish to make arrangements to take back the duplicate...