The three subjects you mentioned, 1650, are definitely public classes that teach in large classes, while the pilot class you cited, 17500, is definitely not a large class, but a high-end class that teaches in small classes. The high-end class can't compare with the popular class. In fact, the pilot class in the big class is not expensive, it is also 1000. Zhang Junfang and Xu Zhiming, political teachers, are famous teachers, as well as Li Yongle in mathematics, Wang Wenke and Wang Yiqun in English and so on. First of all, you have to distinguish whether you go to a high-end class or an ordinary class, so you can compare them.