1, you don't need to spend time looking for information yourself. Classes generally purchase materials in a unified way. Even if they can't, they will tell you which textbook is more effective, so you don't have to spend time looking for information yourself, and sometimes you will find that the information is incomplete or wrong. The time saved in this way can be directly invested in review.
The teacher's explanation is more efficient than his own study. Because teachers are generally more experienced and know where the difficulties are, you don't have to explore for yourself, which will be more efficient and effective.
However, if you apply for classes, the cost should still be relatively high. It is more beneficial for you to make your own choices according to your own situation.