Looking at the average salary per contract of the non-star starting centers (excluding old guys and rookies) there seem to be 2 groups:
1. Centers that can shoot 3-pointers or pass: Sabonis (47), Sengun (36), Porzingis (31), Hartenstein (29), with the exception of Wendell Carter (18) and Turner (19).
2. Traditional defensive centers only - Allen (28), Claxton (23), Capela(22), Zubac (20), Poeltl (20), Adams (13), Gafford (13) , with the exception of the multi-DPOY Gobert (37) and the overpaid Ayton (36).
Kessler is definitely in the second group and he is unlikely to become a 4-time DPOY, so realistically his value is somewhere in the 20-28 million range.
I think 20-25 Million is where the Jazz probably start negotiating, but this is all old money. There will be new contracts signed this year that will keep pushing the average up. You also pay a premium for youth.
It's interesting because the Jazz both seem very far away from needing someone like Kessler, but also not in a position to care too much about the tax.