Why is the price of LED phosphor as expensive as gold?

The patent fee is too expensive. Phosphor packaging for white LED is a patent of Riya. However, some domestic manufacturers are also trying to develop new technologies recently. Let me introduce two kinds to you. One is to coat fluorescent powder on the wafer after epitaxial growth, and white light can be made without fluorescent powder after post-treatment. This patent belongs to Li Zhenming Group, and the other is to combine RGB with three colors to form white light. However, this technology is a failure. Lamps made from different angles have different light colors.