Player value

I'm currently managing Real Oviedo in the La Liga 2021/22 season. I wonder why my players' value never go over 10 millions euro? For example I have this spanish wonderkid that've come through my academy. 19 years old and a right back. Value? €3 mill. Same goes for another wonderkid striker at 19 years old. What does impact the player value? They all have long term contract and a € 60 mill release clause.

My current most valuable player is Adama Diakhaby at € 10 mill.

Does seem strange and can only possibly be linked to the reputation of your club, but on the other hand they are still very young and will certainly see their value increase a lot if you play them regulary so they can improve.