It is easy to estimate the profit of a crime in cases of rapacity, but how are we to ascertain it in those of malice and enmity?

The profit may be estimated by the nature of the mischief that the offender has done to his adversary. Has his conduct been more offensive than painful? The profit is the degree of humiliation that he believes his adversary to have undergone. Has he mutilated or wounded him? The profit is the degree of suffering he has inflicted.

In this, in his own opinion, consists the profit of his offense: if then he is punished in an analogous manner, he is struck in the most sensible part, which has, so to speak, been pointed out by himself; for it is not possible but that the mischief which he has chosen as the instrument of his vengeance, must appear hurtful to himself.

RP Book 1 Chapter 6