Originally, in southeast asia, the white elephant was a sacred animal; emperors took pride in owning one. But owning a white elephant was very expensive and once you had one you could not use it for work or give it away. So the term white elephant came to mean something expensive to keep, impossible to get rid of, and useless to have.
The title is from the exasperated expression : "Money (or any other item that is in short supply) doesn't grow on trees!"