Some students are concerned that open source software and content - text, audio, video, images mean that the author / producer must work for free and are therefore losing money. However, just because the information is free, doesn't mean that the author / producer isn't paid.
There are many different ways to be paid. Some are paid by a company or a college to do the work as part of their job. For example, the college gets student fees, attracts students, get recognition. They get grants from government or foundations or even companies to produce the work and make it freely available. There are many organizations and individuals who believe it is in the best interests of society to make information available freely to anyone and everyone.
Even for this class, the cost of the textbook is much higher than the student fees. We are working to find a better, free or cheaper solution. Others share this concern and are actively doing something about it!
The College Open Textbooks project is working on this.