Found this article today: Desalinating Water Is Becoming “Absurdly Cheap” - Human Progress
The Sorek B plant has a capacity to desalinate 52.8 billion gallons a year and is contracted to produce water for $0.41 per cubic meter. There are around 264 gallons per cubic meter, so this puts the cost at about a penny per 6.4 gallons.
Why are we not desalinating more water in California?