What is the classic example of paradox of value?

It is a known fact that the water that people can drink and use has considerably lessened over the past years. There was a time when clean water was abundant and it will be easy for people to get water that they can use for their different needs.

Over the past years, water has started to become scarce yet it is still not worth as much as the diamond. There are some reports that diamonds are starting to become more abundant. The fact that it is common should have lessened its value but it has only gotten higher over the past years.