Every deal involves a risk, every signing could be a flop. In my opinion we're taking a step ahead by doing this signing, being willing to bet so much money on a kid that has so much talent is a risky bet, but if we succeed on it it could be very well paid.
Per example, City with Agüero, of course that el Kun was on a different level than Dybala, performing for years with Atletico, winning some important titles (Europa League), but nonetheless it was an important bet of a big amount of money.