I can only see one thing potentially going wrong, and that's him just failing to settle at a much bigger club and looking overawed. But that looks unlikely given how comfortable he looked on his England debut. We already know he has the ability. He's performed well and will improve with age. Catastrophic injury is covered by insurance.
There's also the scarcely mentioned matter of inflation to consider. Prices have risen steeply for the last 20 years, and the growth in popularity of the game shows little sign of slowing down. Therefore it seems reasonable to me to pay still more over the odds for a player with a great deal of longevity to offer, because the money you're paying out for him to be playing 10 years hence in terms of this transfer fee would buy you much much less if you were spending it 10 years from now. The last thing you want to be doing in a high inflation environment is sitting on cash, as Arsenal apparently have. You're much better to blow a few million on an overpriced youngster like Shaw.
