well, look to Pogba case, u21 can be taken by other clubs who offer more
24T is high end player, who will develop very very fast .. you are paying what he worth .. 25T if you exchange it in $ section, will equal around his exact value.. this mean you are getting a special player without a Token war .. try to buy this in market, and you will pay:
5-15 (T) + his price will be even higher 150% = so overall you will pay between 40-50T for him in market if we counted how much he worth and extra you are paying .. bcz remember $= Tokens