There is no profit or gain when one exchanges the agreed upon value (supply-vs-demand) of their work/labor directly for Lawful Money of the United States, instead of choosing to accept Federal Reserve issues of intangible "bills of exchange" known as FRN's.
It is a 1:1 exchange transaction like you had stated above.
Every human+being has always had the unalienable natural law (God's perfect Law) right to contract with others to exchange the mutually agreed upon value of their limited resource work/labor directly for whatever form of payment they so choose to accept.