Madrid secured the 23-year-old from Monaco after the World Cup, but the sum has been criticised in various quarters.
Valderrama, however, has said that the attacker is worth the significant fee.
"James showed his quality in the 2014 World Cup in Brazil," he is quoted as saying by AS.
"The mere fact that he has adapted to an important group of quality players who are already established, has merit on its own. And for one so young like he is, even more so.
"It's an important period for him to learn. [The transfer fee] is a normal figure. Madrid paid what James is worth. Now it's his chance. He's 23 and hopes to last at Madrid for a long time."
James has scored three times in 12 games for Madrid this season.