If you look at the price of Tesco 'white label' coke and lemonade (15p for 1.5l IIRC) this would imply that the raw cost of bottling and distributing fluids is somewhat less than this when done in volume. But of course if you put identical water in 15p and £1 bottles people would swear that the latter tasted infinitely better. If it (water or inhibitor) is expensive it must be good!