According to http://waterfootprint.org/media/downloads/Report14.pdf it requires 140 liters of water to produce 1 cup of coffee. The most expensive source of water that I can think of, from a reverse-osmosis desalinization plant, costs $0.40/1000 liters in Singapore (Hyflux, 20 year contract), - so that cup of coffee has a ceiling of about $0.08/to produce in terms of the cost of it's water content.
The question should never be "how much water to produce this" - but, "what value are we getting from the water" - if you are able to sell a cup of coffee for $5, then it's probably a good investment of that $0.08.
The question should never be "how much water to produce this" - but, "what value are we getting from the water" - if you are able to sell a cup of coffee for $5, then it's probably a good investment of that $0.08.