Then they calculate the quid pro quo; thus Python and Pammenes quarrelled; and so do teacher and pupil (for knowledge and money have no common measure), and so Herodicus the doctor quarrelled with a patient who paid him only a small fee; such too was the case of the king and the lyre player; the former regarded his associate as pleasant, the latter his as useful; and so the king, when he had to pay, chose to regard himself as an associate of the pleasant kind, and said that just as the player had given him pleasure by singing, so he had given the player pleasure by his promise.