I don't have any figures, but that's not universally true. Pirating is so much easier and more convenient than purchasing, it's often the more favorable option. To me, iTunes Plus makes pirating music pointless.
Whatever the number is of people who both can afford to pay and choose to pirate, it's hardly big enough to bring down these companies, and as near as I can tell copy protection only makes it worse. None of these copy protection measures have prevented, or, it seems, at all deterred the availability of pirated content--and if it isn't doing that, I really don't see the point. All it does is prevent people sharing with friends. I don't believe in that. On the other hand I'm not in charge of maximizing profits at a record company or film studio.
What is this fascination with maximizing profits? I would think it would be more gratifying to one's vanity to be known as a saint, rather than a billionaire.