Huh? There's plenty of water, endless water. It's cheap-because-drinkable water that isn't aplenty.

On the Moon, this is what may be lacking.

On Earth, we can close loop recycle from drains. We can take sea water and desalinate. We can use osmosis and clean dirty ground water.

Is any of that cheap? Nope. But it's also not a blocker on having water to drink and bath with.

We will never run out of water, only "easy clean water".