because better potential he has, more salary he demands.
better is the player(if you train properly)
If I continnue to always train star potential player,I will never raise to the top division,so a star player for me it's useless both to have them in my team and/or to sell them.
To raise the level of my team,I need to train better players,then if I fail to be promoted I will sell them and I will start to train new players.But star player will not improve my team or every team of a medium division and will not have good value on the market(being also older than players with the same skills)
10k more in merchandising are not worthing all the things I wrote
The 19yo at the time are useless,if you raise their level,at least you earn in short period what you lose in the long period