The common price of a slave during the time of Jesus was 30 pieces of silver, the same price Judas was paid to betray our Lord with a kiss.  
<a href="http://dogwooddaughter.bandcamp.com/track/live-and-forgive" mce_href="http://dogwooddaughter.bandcamp.com/track/live-and-forgive">Live and Forgive by Dogwood Daughter</a>

Lyrics

 
 
For thirty pieces of silver
Lord Jesus was betrayed
For thirty pieces of silver
The common price of a slave

For thirty pieces of silver
 Judas sold him out
For thirty pieces of silver
  He wore a thorny crown

For thirty pieces of silver
They beat and spat on him
For thirty pieces of silver
Lord was condemned

For thirty pieces of silver
Our Lord was crucified
For thirty pieces of silver
His mother mary

But all the silver in the world
Could never satisfy
The tortured soul of Judas 
Who hanged himself and died