The same course content can be set up as self-study classes or interactive classes.
A self-study classes has very little interaction with the instructor. The instructor feels that the course content is good enough that there is no need for a lot of instructor interaction. Self-study classes are usually prices less than interactive classes.
The same course content can can also be set up as an interactive class. In this case the instructor has more personal contact with his students. There can be live video chats, video or written homework assignments, module forums where the instructor can define the topic and answer student questions posted in the forum etc.
Interactive classes usually sell for more money because the instructor spends more time administering the class.