Money represents obligation. Either to give somebody a puns of silver or to provide a negotiated amount of value. That value need not be scarce, as in the case of say, a downloadable audiobook or music file.
For something like silver/gold, the scarcity is around labor to discover/mine/refine it. If it was free to mine silver, it would not be worth any money/obligation.
You have to go one level deeper with something cloneable, but there is still scarcity.
The cost of a downloadable audio book is going to be based on maximizing the return based on its demand curve (since the supply curve is vertical).
The demand curve is going to be based on the scarcity/cost of an equivalent value audio book (if an audio book is $1000, you'll probably buy a different one from another author instead). Thus, this ties back into the scarcity of supply, which is tied to the scarcity of labor (skilled in this case) to generate that supply. There is a certain amount of labor required to become skilled (and to a lesser extent scarcity of talent), and more labor to produce an audio book. This scarcity of labor keeps audio book prices from dropping to zero.
You have to go one level deeper with something cloneable, but there is still scarcity.
The cost of a downloadable audio book is going to be based on maximizing the return based on its demand curve (since the supply curve is vertical).
The demand curve is going to be based on the scarcity/cost of an equivalent value audio book (if an audio book is $1000, you'll probably buy a different one from another author instead). Thus, this ties back into the scarcity of supply, which is tied to the scarcity of labor (skilled in this case) to generate that supply. There is a certain amount of labor required to become skilled (and to a lesser extent scarcity of talent), and more labor to produce an audio book. This scarcity of labor keeps audio book prices from dropping to zero.