I wonder if this is true of all artists. Here is a question posted on his Website:
Tim Sloane of Ijamsville, MD asks: Al, which of these purchasing methods should I use in order to make sure the most profit gets to you: Buying one of your albums on CD, or buying one of your albums on iTunes?
I am extremely grateful for your support, no matter which format you choose to legally obtain my music in, so you should do whatever makes the most sense for you personally. But since you ASKED… I actually do get significantly more money from CD sales, as opposed to downloads. This is the one thing about my renegotiated record contract that never made much sense to me. It costs the label NOTHING for somebody to download an album (no manufacturing costs, shipping, or really any overhead of any kind) and yet the artist (me) winds up making less from it. Go figure.
Don’t ask why I was on Weird Al’s Web site.