It's going to be 50 million + bonuses. Brescia are going to get relegated, and he won't want to stay there.
Magotta won't engage in bidding wars (we know this) and I doubt the kid wants to leave Italy.
Tbh, I'd even consider selling Pjanic for the right amount if Bentancur keeps developing. A midfield of Pogba/SMS, Bentancur, Rabiot, with options like Tonali, Kulu, Ramsey, and even Burnturdeski off the bench is quite enticing.
The summer of 2020 must be when we finally upgrade that midfield. Boubakary Soumare is also a very interesting option, but he seems EPL bound