Because of the way young lads are coached these days with 'false 9s', playing with two no.10s, High press, packed midfields etc out and out centre forwards are becoming rarer and rarer. Its no surprise that anyone these days that puts a run of 10 or more goals together is being quoted in the £50m+ bracket. I mean look how desperate Arsenal and West Ham currently are for a striker.
Personally, within reason I'd give JPM what he wants to extend. I'm not convinced by Nketiah and I think he would be very difficult to replace. I can think of a few clubs (some very big ones) that would love to have him. I can see a big bid coming for him in the summer if he hasn't extended and his form continues.