Stallman was not talking about cost in $$$ or effort. He was talking about "freedom" (free as in speech). He believes that there must be some piece of code in Firefox that is tied into some corporate governance which does not allow people to take, use, modify, distribute, etc, etc.
It's really a sorry thing. Back in the day when FOSS was getting started, people like Stallman were critical. The community needed people like him to ensure that FOSS started free and stayed free. It kept the corporate money mongers at bay and made sure free software (as in speech) had a place to grow and mature. Every time there was an encroachment by somebody trying to corrupt that, the GPL and other such licenses were there to push back. Unfortunately, it seems that lately Stallman and his crew have gone beyond simply "protecting the idea" and have moved into fanaticism. This could be potentially dangerous for the community. While many view Stallman as a crackpot, he really has been critical to the open source community. Sometimes, an idea needs an empassioned person to keep the fire alive for the good of all. But if he really does go further around the bend and really does become a raving lunatic, conspiracy theorist, a true wackpot: then he will simply be ignored, even by his own FOSS community. Then he will be irrelevant, and the staunch support of the open source ideal will be marginalized, and then FOSS will have no protectorate. Stallman is hurting his own cause, which does make me concerned for the community as a whole.