If California ratepayers were asked whether residents and businesses should be forced to pay more than the reasonable cost of delivering water to their taps, I’d bet my bottom dollar that virtually all of them would respond in the strongest possible terms: That’s not fair or legal. Essentially the same question is at the heart of the San Diego County Water Authority’s July 31 petition for review by the state Supreme Court: Can the Metropolitan Water District of Southern California charge San Diego County more than the cost of providing the services we purchase?