I don't understand the financial concern at all. How could increasing the water supply increase the price? It only makes sense to me if the price is artificially low right now.
Environmental damage by a desalinization plant couldn't possibly be worse than overdrawing the acquifer -- the defacto solution.
Because California has plenty of water for residents. What California doesn't have is plenty of water for agribusiness.
And the agribusinesses do NOT want people paying close attention as all the valid solutions to water problems are basically "shut down agribusinesses in arid areas".