Thanks Rotormatic. Very in depth.
There are obviously aircraft out there that are alot more cost effective per gallon/litre of water than many others and by the sounds of it the FireHawk is one of the cost effective ones.
Of course we can't all have these big machines flying around dropping huge amounts of water and many places only have access to the smaller AS350, BK117, B205, B412 and the like which would have a much higher cost per litre of water than the big machines.
I saw an Aussie news story the other day about two AS350's with water tanks fitted fighting a blaze near Brisbane and the cost/litre per hour for those aircraft dropping 1000 litres would be fairly high. Even worse when you use a B412 dropping 1500 litres!