[chongli]

Your definition of "fungible" applies to literally everything on the planet. Everything can be exchanged for money and back again. That's not what fungible means. Here's another example to help you differentiate:

* Gold is fungible. Any bar of pure gold (of identical mass) is exactly interchangeable and has an identical value with any other bar of gold.

* Diamonds are not fungible. Every individual stone is unique and must be properly graded by a licensed jeweller. Two stones of the same mass are highly unlikely to have the same value.

[WalterBright]

The entire reason markets exist is so people can exchange what they don't want for things that they do want. For the purpose of this discussion, they are fungible.