Ok let's compare just their PL stats since that's all that matters.
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Again 4.5x as many minutes as Cornet for 8 more goal involvements, this includes Iwobi playing for a side that were actually decent once too. In relegation threatened teams Iwobi has 10 assists, 4 goals, Cornet has 1 assist and 9 goals in like half as many games. In other words Cornet must be some sort of magical world class footballer with these stats to even be close to Iwobi or else the reality is both aren't very good footballers but Cornet is clearly far better value.
Iwobi is a useless footballer, £20m + add ons is a mad fee considering anyone with a brain and two eyes can see just how poor he is.