Something very ugly happens when a human life is calculated in money.  It turns people into a commodity to be traded.  His or her value is the highest price anybody will pay for them, in anticipation of getting something out of them.  Exploiting human beings is normal (but not right), in a sinful world where people are greedy for power or profit.  However it is dressed up, it is slavery.  And where people stand in their way, they may pay blood money to get rid of them.  Judas was paid thirty pieces of silver (the price of a slave - Exodus 21:32) so that Jesus could be stopped from obstructing the power ambitions of the religious leaders.  It was very ugly and very wicked.
 
Eventually even Judas realised the depth to which he had sunk.  Although he tried to undo the deal by handing back the money which he had bargained for Jesus (Matthew 26:14-15), the chief priests were not interested.  They had got what they wanted: Jesus in their custody and control.  And now they were going to get what they had paid for – a dead Jesus.   Judas flung the silver coins into the temple and then, remorsefully but not repentant, threw his own life away.  That money gave a problem to the religious leaders: what were they to do with it?  It could not be used for any holy purpose in the temple; it was blood money.
 
Even in the middle of so much wickedness, the answer came in God's Word.  They remembered that Jeremiah had bought a field with silver coins (Jeremiah 32:6-9), and Zechariah spoke against the unfaithful priests of Israel and threw thirty pieces of silver into the temple to the potter (Zechariah 11:10-13).  The chief priests realised that there was a potter's field in Jerusalem: and so they used the money to purchase a burial ground for strangers.  But the real cost of the crucifixion was not paid in silver, but with the precious blood of Christ (1 Peter 1:18-19).  That was the ransom paid to redeem unholy people like us from slavery to sin (Ephesians 1:7), and from the miserable eternal fate to which Judas propelled himself. 
 
It is right that we should be disgusted when we see people exploited, by greedy people who gain from their ugly trade, in many different ways.  We should do all we can to bring justice to the oppressed.  But the greatest slavery is the slavery to sin (John 8:34).  Remember that the Son of God was valued as a slave in order to redeem you from that slavery.  It was grossly ugly, but He did it because He loved us.  Do not treat that expensive love lightly.  "Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God? You are not your own; you were bought at a price. Therefore honour God with your bodies." (1 Corinthians 6:19-20)