@Mikey:
I'm pretty sure anime is a package deal, meaning it's not just bought "all in one" but there are also licensing fees for different parts of the show, such as music. Dubbing companies, most of which in the '90s, took advantage of this and licensed anime without the JP music to save money.
There's obviously some sort of money issue here between FUNi, Toei, and Avex.
From what I have heard, there is really no fee for "background music", so to speak (with very rare exceptions), but there are sometimes licensing complications for the vocal songs, especially songs not produced in mind for the show (such as the Opening and Endings). One Piece has experience the latter here, obviously.