Book I, 349e, Socrates confirming the position of Thrasymachus:
"...is any musical man who is tuning a lyre in your opinion willing to get the better of another musical man in tightening and relaxing the strings, or does he claim he deserves more?" [Bloom, 2nd Edition]
"...any musician in the tuning of a lyre would want to overreach another musician in the tightening and relaxing of the strings or would claim and think fit to exceed or outdo him?”"[Shorey]
"...a musician when he adjusts the lyre would desire or claim to exceed or go beyond a musician in the tightening and loosening the strings?" [Jowett]
This is extended to a medical man, any man with knowledge of an art, and finally the "good and the wise". Book, I 350a:
"Consider then with regard to all forms of knowledge and ignorance whether you think that anyone who knows would choose to do or say other or more than what another who knows would do or say, and not rather exactly what his like would do in the same action." [Shorey]
Book I, 350b:
"Then he who is good and wise will not wish to overreach his like but his unlike and opposite."[Shorey]
People knowledgeable in an art, including music and medicine, do compete with each other. Could Thrasymachus's model be a naïve (or perfected) one where everyone in an art has the same static level of it such the man knowledgeable in an art could (or should) not exceed another without doing something artless, or why else would Thrasymachus agree with Socrates that Thrasymachus's position is they would not?