"Stanley & I have agreed on our policy : Art or Cash. Either very profitable terms indeed; or absolute author’s veto on objectionable features or alterations."

I don't think it was explicitly stated there, but I think it is clear they went for "cash". Though I recall some of his letters saying that the unexpected success of LotR meant that he wished he'd retired earlier. It was clear that there was a lot of financial struggle in his life, but that's not to say he wrote for the money of course!