Yep. It just happens to be 10k for some players and not for their entire career as it changes with their age. It could've even been 10k for your player, I just don't think you'll ever see 5.01M displayed. Some people have even reported value supposedly decreasing when they add skill points - that's not true either. After reaching a certain number, the values are just starting to be rounded more to the left side.
The number that is added is a percentage of the player's value (I don't think anybody knows the exact percent, it's probably dynamic anyway), just like with extending players' contracts - they will always ask "a one time fee" and that fee is always 10% of their value.
You're welcome.
Perhaps you've hit his maximum market value. If you're training him as hard as he can be trained, playing him as much as he can play and there's nothing else that could be done to make him a better player, he's at his peak (for his age and level) and his value won't increase.
I don't know that though. Jus' sayin.