The extra tiny cost is worth that warm fuzzy feeling, knowing that even if I were to *accidentally* put some unlicensed media on those disks, I don't have to worry at all about cheating those RIAA executives out of their second summer home.
Do you think that you're immune to RIAA action in the United States just because the media on which you're using for "accidental" copyright infringement was purchased in Canada? While the Canadian tax on media may provide for safe harbor in that country (I don't know that to be the case, but I'll assume it's true for the purpose of this post), saying that having a copy of Britney Spears' latest album (which you had not already purchased) fresh off BitTorrent on a CD is OK because you paid a tax on that CD in Canada is not going to get you very far in an American courtroom. From the MPAA/RIAA's perpsective, copyright infringement is copyright infringement, regardless of whether it takes place on media purchased in the U.S. or in Canada.
From a purely moral standpoint, your argument is solid. The **AAs are in fact compensated when you buy that media in Canada. However, for those Americans with any legal worries, I would suggest that you discuss the implications of putting unlicensed content onto media purchased (and on which the "pircay" tax appropriately was paid) in Canada with an American lawyer before trying to use the Canadian flag to shield your infrignement activities in the USA.