What does Luke 22:5 mean?

The Pharisees and Herodians have been trying to destroy Jesus since early in His ministry (Mark 3:6). The religious leaders in Jerusalem joined the fight after He raised Lazarus from the dead (John 11:45–53). Their problem is that it's Passover: Jerusalem is filled with visitors and Jesus is becoming more popular every day. The religious leaders can't figure out how to grab Jesus without antagonizing the crowds. They may be high-ranking priests, teachers, and businessmen, but they are still vulnerable to both public opinion and public violence (Luke 22:2; Matthew 26:3–5).

Their luck changes when one of Jesus' primary disciples comes with an offer: he will safely lead the temple guards to Jesus, in private, if they pay him. The chief priests are thrilled. They get more than they had hoped: an opportunity to hide their deeds from the crowd and a scapegoat if they're caught. They negotiated a price of thirty pieces of silver. This was the price of a slave in the Old Testament (Matthew 26:14–15; Exodus 21:32).

Judas consents to the price and watches for an opportunity (Luke 22:6). He knows that even though Jesus is surrounded by adoring crowds during the day, He retires to the Mount of Olives at night (Luke 21:37–38). Judas doesn't have long to wait.

That the chief priests and officers "agreed" means Judas at least suggested the payment and might have haggled for it (Matthew 26:15).