The answer has little to do with whether people are paying you for what you do.
I think the most appreciable distinction between a true professional and an amateur is this:
A professional is presenting a self (consistently and deliberately), while an amateur is revealing the self they feel like being in the moment.
Imagine the waiter/waitress that served your last coffee. If you have been as lucky as me, then s/he was accommodating, pleasant, and even went the extra mile to pull the chair for you. Now, suppose s/he has had a horrible morning. Perhaps s/he had to deal with less than well-mannered patrons. What, then, explains her kindness? Even more importantly, is her kindness “authentic”?
Of course it is not authentic.
Because s/he knows that when she on her mission as a true professional, s/he does not reveal her authentic self. S/he merely presents a self – the self that you expect to see. If one single phrase could sum up professionalism, then this would be:
Your mission is greater than your feelings.
