One day we'll have the ability to copy physical objects just like we copy files today, and it would be as cheap. In fact we may see that technology in our lifetime. At that point, the whole concept of "stealing by copying" would be challenged as never before, and I believe it will surrender. All ethical or business issues aside, it will surrender for two simple reasons: (1) it would be practically impossible to prevent copying and (2) it won't actually do any serious harm to the author who considers herself to be "robbed" through copying.