I wouldn't judge the lad too harshly. I don't think any one knows his true motive, whether it be money or an increased chance of first team football.
Even if it is more money, we know the fickle world of football, and many young kids who you think will make it, never even get the chance and are moved on for very little or even get another team. who can blame him too much if he wants to make hay while the sunshines. If he does break through, then also suggests the investment in him was possibly worth it, like Pogba.
But on the other hand, you can't hold on to every player "Just in case".