i would guess most of the money related to someone like Hwang Hee-Chan would be merchandising.
He is probably the second or third (or maybe 4th), most marketable South Korean player, and only those 4 are probably marketable in any major way, for a country that has 50m+ people in it.
very shrewd tbh, imagine if the English only had 4 good players, and the whole country of football fans followed one of those 4 players closely, bought merch etc, lots of cha ching.
i always remember that Japanese famous player in the early 2000s (Nakata), i remember reading about it, and the clubs that paid transfer fees for him (Parma/Roma), said they made more in merch from him than they paid in transfer fees etc, and they both paid 20m+ for him, back in the early 2000s.
I have said it before, Villa needs to get on the Asia/Japan/Korea player bandwagon, or try to.