Tomori completed a permanent €29m move from Chelsea after a six-month loan spell at the San Siro.
The English centre-back is the most expensive signing so far after Fiorentina’s Nicolas Gonzalez, who has joined the Artemio Franchi for €23m from Stuttgart, signing a five-year deal with the Tuscans.
Juan Musso’s €20m Atalanta switch is the third most expensive signing in Serie A so far, followed by Matteo Politano and Weston McKennie.
The Italian winger completed a permanent €19m switch to Napoli this past February after his first appearance with the Azzurri in the second part of the season.
Back in March, Juventus announced McKennie’s permanent transfer to Turin for €18.5m plus potential €6.5m bonuses.
Hamed Junior Traoré, brother of Manchester United starlet Amad Diallo has joined Sassuolo on a permanent €16m deal from Atalanta this summer and is the sixth most expensive signing in Serie A so far.
Musa Barrow’s €14m Bologna switch, Mike Maignan’s €13m move to Milan, Rui Patricio’s €11m transfer to Roma and Razvan Marin’s permanent move to Cagliari for €10m complete the top 10 of the most expensive transfers in Serie A so far this summer.