Institutio Oratoria

To conelude, then, the orator will not seek to make more money than is sufficient for his needs, and even if he is poor, he will not regard his payment as a fee, but rather as the expression of the principle that one good turn deserves another, since he will be well aware that he has conferred far more than he receives. For it does not follow that because his services ought not to be sold, they should therefore be unremunerated. Finally, gratitude is primarily the business of the debtor.