Radiohead's lawyers and publishers released a statement in response to this whole fiasco, if you want to read it.

Basically, what people are now inferring is that this isn't about the money so much as the songwriting credits. Radiohead originally asked for songwriting credits and probably a small royalty because in their opinion, the verse of Get Free sounds too much like the verse and chorus of Creep to be a coincidence. Lana is refusing to give songwriting credits because she says it's her own original work, but is willing to give a larger royalty (40%) to make them happy. Radiohead/their publishers, however, want credit, not just money, so they're using the 100% as a bargaining tactic to basically say, "Look, just admit that you plagiarized some of your song from us, or else we're not going to let you profit off of it."

I hope that my explanation doesn't seem too biased: As you can tell by my username, I am a Radiohead fan, but I easily understand both sides of the issue and hope they can find some kind of compromise.