Originally Posted by aerobod

To take a bit of the magic out of the free water:

- a high proportion of the guests will take a water service on a long haul flight.
- the water will be carried anyway, but usually in the 2 litre Dasani bottles (Coca Cola is the current WS supplier), as opposed to the mini 0.3 litre ones.
- most of the cost to supply the water is in carrying it's weight on a long haul flight, about $0.50 for 0.3kg of water as a portion of the payload.
- supplying the water in 0.3 litre bottles compared with 2 litre ones likely increases the cost by about $0.25 per litre due to the increased packaging.
- putting a bottle at each seat before flight probably doesn't take any more labour time than pouring the water into a glass from the cart.

I would estimate that WS can probably do this for less than $0.10 per guest when the whole process is taken into account.