i always find it very hard to put a price tag on players, especially young players. He gave some signs of potential with cercle brugge last season, and is doing fantastic know, but to really make an honest assesment of his quality I'd say it's too soon. He, like Lukaku and De Bruyne, still have alot to proof.
A little off topic, but I have bad news about De Bruyne: he's a Liverpool fan