Pricing water appropriately would be great, but there's more to this issue than that. In a nutshell: what is the value of keeping a fish species from going extinct? That's a policy question requiring public debate.
Maybe everyone should just move out of California. Or perhaps they could all just euthanize themselves? That would save a lot of water. Certainly saving six fish is far for important.
They should mandate water supply for endangered species and then after that price water at the same price for everyone. Much of the current agriculture would become unviable and the farmers could switch to either less thirst crops, growing somewhere wetter or just get some comp and do something else. Agricultural water use would plummet. Problem solved. Apart from politics of course.
