[ygra]

I guess they meant getting the drinking water to the space station in the first place. Water doesn't really compress well (unlike the hockey puck rag) and also weighs quite a bit so sending it up should be pretty costly.

[akadruid1]

very roughly, water is $50 million per tonne on the ATV, so (even more approx) $30,000 for the water used in the video.

[tempestn]

Hydrogen and Oxygen compress though, and are combined into water in the station's fuel cells.

[jfim]

You still need to carry the same mass of hydrogen and oxygen than the resulting mass of water, though.

[tempestn]

Mass, yes, but saving volume is also beneficial.

[quesera]

It's safe to assume that there is water on premises for other reasons.