Last year Fiorentina offered 28m iirc and Sassuolo didn't even entertain the offer.
After a great statistical season he had I cannot imagine anything less than 40m which is fucking nuts
Berardi would be fine if we were in 2011 territory and we needed an established Serie A player for 15-ish million to be the bridge between getting back on level in Serie A and then improving. But for 40m he is your investment for now and the future. That's crazy