I actually dont think their values are too far off (Bayern playing the extra €10 million is insanity). I think Chiesa is probably in the €30-35 million range and Kimmich is the €40-45 million range, as both only have 1 year left on their deals and Kimmich will be going into his age 30 season.
That being said, Kimmich is on massive wages that Juventus wont come close to matching, not to mention I highly doubt he's looking to leave Bayern to join a club that is in the process of trying to build itself back up to compete to win Italy, much less Europe.
If Kimmich leaves Bayern, he'll be joining one of the top clubs in Europe, and probably to play as a midfielder.