1. Resource allocation: Zhu Junwen is a well-known builder training lecturer, and he may allocate his time and energy to other contents or subject explanations according to his own needs and course arrangement.
2. Subject requirements: The cost may involve many specific professional knowledge, such as economics and engineering technology. This may require Zhu Junwen to have corresponding professional background or specific qualifications.
3. Market considerations: The theme of cost may not be of concern to his main audience or the market. The market can choose and adjust the course content and lecturers according to needs and interests.
4. Personal reasons: This may also be Zhu Junwen's personal reasons. For personal reasons, he may decide not to explain the cost.
The above only outlines the possible reasons, and the actual situation may be different due to personal and market factors. If you regret that Zhu Junwen has not paid the fees for 22 years or need further information, I suggest you consult the latest training resources for builders or consult relevant training institutions.