“The common law defense of frustration of purpose arises from the occurrence of an event causing a failure of the consideration for the contract or a practically total destruction of the expected value of the performance. Unlike cases of impossibility, performance is admittedly possible in frustration cases, but the anticipated value of the performance to the party seeking to be excused has been destroyed by an unexpected event that causes “an actual but not literal failure of consideration.” ‘Mere difficulty, or unusual or unexpected expense does not establish frustration or impossibility of performance of a contract.'”
[California Affirmative Defenses [certain citations omitted]]
