AllOfMp3.com charges by the megabyte! One or two cents a megabyte. And you can choose the bit rate, so if you want a crappy file, it's cheaper than a high bit rate file. But at these rates, why wouldn't you grab the best quality you can? And there is no DRM.
I was pretty sure this site must be illegal, since I bought a song for less than 4 cents. (They do math down to the 1/1000th of a cent, because they can.)
They have songs you can't get in the US.
The review above claims it is all legal due the vagaries of international copyright.
Now that's amazing.