How about this. Maybe could be done these demands for wage more elasticly. So once is that player in lower league for a while, he get used to a cheaper life. But once he gets first league, his demands will increase by the time.
So if he is transferlisted afterwards into lower league, will take some time before he gets into lower wage level.
This create two things. Players which will be transfer listed by high-league teams, will be kind of cheaper and these which goes out of bottom league, will have kind of bigger price, because of theirs salary.
That would possibly create enviroment, where would be biggest stars affordable for everyone. Especially for a first-league teams, because once are these wages setted by the way that lowleague team can hardly afford 1 player like that, whiile temporary this wage would be kindly acceptable by 1st league team, it could work.
Imagine something like this. There is a first league team which have maximum space for such a player 250k. There is a 3rd league team which have space like that 100k.
There will be a star which in 3rd league earns his maximum - that is 100k. If such player buy 1st league, his demands would increase into 250k for a 3-4 seasons before he would go into 250k and aditional 1-2 seasons before he would get his maximum 350k (for example).