I'm tired of the term "artificial scarcity". First, do you understand what scarcity means? The supply of content is unlimited. Putting a price on content is not creating "scarcity". Consumers make content purchasing decisions based on the scarcity of their own resources. Second, what is non-artificial scarcity? All scarcity is artificial.
I think the term is being used to note that the price is artificially high - supply is virtually limitless once the first copy of the song is created, so the price should approach zero.