“Why is gold more expensive than water that we can live without?
As a first observation, gold is rarer than water; most of the time, the price of a material depends on its abundant, the cost of isolating it and make it available, and last but not least, on its importance at the moment. Gold is rarer than water, thus is more expensive.

However your life is more valuable than anything and if you are thirsty and water can save your life, then water is more valuable than any gold and you are ready to give it for water; in the end, if you die and you have the gold of the world, so what, you are still dead.

You want to see which is more valuable? Put a group of people somewhere where there isn’t enough gold. And put another group of people where there isn’t enough drinkable water. The first group will never even notice their dilemma. The other group will, literally, murder each other over the drinking water.

Gold ain’t nothing. Drinkable water… now that is valuable.

Because water is more plentiful. If gold literally rained down out of the sky, it would be pretty cheap too.

There is no inherent, cosmic price for anything. The monetary value is based on what people will sell it for and what people are willing and able to pay for it, nothing else. That number is nominally set by supply and demand. How necessary something is for our survival tends to do a lot to set the ‘demand’ side of the equation (and the demand for fresh water is huge and never-ending) but that tells us nothing without the ‘supply’ side.

Gold is rare, water is wildly common. Water is more ‘valuable’ in the sense of being more needed, and that we’d miss it more if it were suddenly gone. But in terms of price, gold sells for more money because people can charge hundreds of dollars an ounce and other people will pay it. And they’ll pay it because there’s no other source where they can get it substantially cheaper. If you had the only water in the world, I’d pay more than gold for it to keep myself and my family alive. But as things stand, I have no reason to pay you that much for water, because I can just catch it when it rains.”