I think thats because normally 1st league team cant afford 150-200k player like that, so it is about teams which have no other perspective, to pay them.
The percentage cut is giving a greather bonus for the players with higher wage, because it shut down bigger cut. Thats why would this solution kind of balance theirs demands.
So if there are any specifications used as a variables for merchandise and 380k player gives to the club more than 150k player, it is maybe still not enough. (at least for small countries, where farming will be always needed)