You are fully aware that you can offer work in exchange for things rather than gold or fiat money?
From the other link we'll find
>Free workers were even recruited from neighbouring satrapies at harvest time (Dandemaev and Lukonin, 1989: 157). Paid free-born labourers worked on the Babylonian canals, and free non-citizen farmers worked the land of the state, temples and the rich (Dandamaev and Lukonin, 1989: 152), and provided the corvee labour at such sites as Susa and Persepolis (Kent 1953DSf 22-58). They could not be sold, and so were not actually slaves, and could be considered non-citizen workers.
(my emphasis)
The discussion is more complicated than quoting a couple of random non-related articles on the Internet. But simply changing the meaning of a given statement and dismissing the entire counter argument is dishonest.