"An exit from the world’s biggest Internet market would cost Google, whose sales growth slowed during the U.S. recession, $600 million in revenue, according to estimates by JPMorgan Chase & Co."

On the other hand, I wonder how much it's costing them. Once you add in all the costs of filtering the Chinese searches, I could see them not making as much profit as you'd expect. But this is sheer conjecture on my part. It's also possible that Google's bluffing.