A significant majority of the time when I want to purchase MP3s from iTunes it is cheaper for me to purchase the CD from Amazon and have it shipped to me, then iTunes match it. I've got about 80 or so CDs I've done this with.

I don't know if I'm exploiting a loophole or not, but I figure because I have the physical CD at my desk, it's legit. I'm still uncertain if this is shady behavior on my part or not - but I save $2-$3 / CD, so I keep doing it.