In the last three decades, the cost of desalination has dropped by more than half and more plants have come on line. California, for instance has 11 plants with 10 more proposed. The water costs about twice of that from other freshwater sources. Guess that would double my water bill from $30 to $60 a month - certainly affordable (btw, Israel gets over 1/2 of its water from desalination and the average bill in 2016 was $30, about the same as the U.S.).
That is not to say that desalination doesn't have issues - It does take energy, but a lot less than it use to, and for every gallon of freshwater, a gallon of higher brine seawater must be disposed of. Still, the point is just like gains in solar panel efficiencies have boosted solar production as being more cost-effective, so has gains in desalination efficiency made this option quite viable (and needed).