Say you are a 3 million lb. walnut grower... Your neighbor is also... He sells his nuts for $1.20/lb. and receives $3,600,000 for his crop... You, great guy you are sell to Diamond, and receive $.85/lb. and gross $2,550,000. Who cares about the contract, you walk!
If a grower has a 5 or 10 year contract with Diamond and agrees to the terms, I would think Diamond has significant recourse. Yes, walnut prices can fluctuate from $0.75 to $1.30 in a year. That's the nature of the business. Growers know this and thats why they agree to the exclusive contracts.