It's all a crapshoot, but offering 90% is way too much.
Imagine that you have 10 guys demanding $6M and offer all of them $5.4M- you win 5, that saves you $3M. Now suppose you offer them all $4.5M- you only need to win 2 to save the $3m (highly likely) and there's a good chance you win 3 or 4 cases to really free up an extra wad of cash.
I probably normally offer 75%- win less than half- maybe 1/3. But that's still going to work out better than winning half of your cases at 85-90%