Which class is the tuition fee for?
Which "lesson" does the "lesson" in "lesson fee" refer to? Many people intuitively think of "class" as "course", but in fact, it is closer to "class" as "taxation". Game developers use the "fee" system to charge additional fees to players in exchange for advantages or conveniences in the game. This is just like government taxation, a disguised "charge" aimed at making profits.