Or he could be effectively worthless if his performances revert to the Newcastle game and before. I'm not advocating selling him, but £15m seems about right given his development so far, there isn't a club on the planet that spends £20m+ on him at this point in time. Maybe he kicks on and he's worth £25m like you say, maybe he doesn't and he leaves for free in 18 months time. I can see the argument for flipping him for a decent PSR profit now when he's not a first choice player for the team in 11th place in the PL.