The song describes how workers were not paid cash; rather they were paid with unexchangeable credit vouchers for goods at the company store, usually referred to as scrip.    From Wordnik.com.  [WN.com - Business News] Reference

But abolish labor, and you have left only articles of greater or less usefulness, which, being stamped with no economic character, no human seal, are without a common measure, -- that is, are logically unexchangeable.    From Wordnik.com.  [System of Economical Contradictions: or, the Philosophy of Misery] Reference

Thus, so much of every product as is rendered by excessive abundance inconsumable, becomes useless, valueless, unexchangeable, -- consequently, unfit to be given in payment for any thing whatever, and is no longer a product.    From Wordnik.com.  [What is Property? An Inquiry into the Principle of Right and of Government.] Reference

If the public, who are free to purchase it, refuse to do so, it is clear that, the poem being unexchangeable, its intrinsic value will not be diminished; but that its exchangeable value, or its productive utility, will be reduced to zero, will be nothing at all.    From Wordnik.com.  [What is Property? An Inquiry into the Principle of Right and of Government.] Reference

(excess) of being: place that cannot be known unexchangeable excess tamed into exchange.    From Wordnik.com.  [Serendip's Exchange -] Reference

"assets" that have flooded banks and institutions become "toxic", unquantifiable, and unexchangeable, capitalism can't work well simply because capitalism depends on a certain degree of confidence in the system, in its players, on a well-defined value of assets, on easy enough trade, and on the positive value of most companies 'actual assets - much like life depends on constant laws of Nature, well-defined numbers of copies of DNA molecules, the ability of living creatures to move, and the "alive" (as opposed to "dead") status of most animals in Nature that haven't yet been eaten or recycled.    From Wordnik.com.  [The Reference Frame] Reference