Money isn't an illusion. It is a useful abstraction of human effort/potential. The workers will be fired because the boss has run out of societal-effort credit

Money isn't an illusion. It is a useful abstraction of human effort/potential. The workers will be fired because the boss has run out of societal-effort credits. The only "illusion" is the collective understanding that these "made-up" credits can be redeemed with other counterparties for human effort in the future. So long as we all approximately believe that idea, it works.