Thirty pieces of silver was the price for which Judas Iscariot betrayed Jesus, according to an account in Matthew 26:15
15 “And said unto them, What will ye give me, and I will deliver him unto you? And they covenanted with him for thirty pieces of silver”.
Before the Last Supper, Judas is said to have gone to the chief priests and agreed to hand over Jesus in exchange for 30 silver coins, and to have attempted to return the money afterwards, filled with remorse.
This event seems to be a partial fulfillment of the prophecy in Zechariah 11:13, although the reference is only a general statement, rather than an actual quote. The main point of the reference is to explain the use of the money to buy the potter’s field, a fact not prophesied by Zechariah (Matthew 27:6-8,10). Jeremiah, however, does mention buying a field for silver (Jeremiah 32:6-9), and Matthew conceivably could have had both passages in mind, giving Jeremiah priority for the general idea, since he was the major prophet of the two.
Jesus was then arrested in Gethsemane, where Judas revealed Jesus' identity to the soldiers by giving him a kiss.
According to Chapter 27 of Matthew's gospel, Judas was filled with remorse and returned the money to the chief priests before hanging himself. The chief priests decided that they could not put it into the temple treasury as it was considered blood money, and so with it they bought the Potter's Field.
A different account of the death of Judas is given in Acts of Apostles; it describes Judas as using the money he had been rewarded with - no sum is specified - to buy the Potter's field, and then falling there, dying of the resulting intestinal injuries.
The word used in Matthew 26:15 (argyria) simply means "silver coins".
There were a few type of coins that may have been used. Tetradrachms of Tyre, usually referred to as Tyrian shekels (14 grams of 94% silver)
Staters from Antioch (15 grams of 75% silver), which bore the head of Augustus.
Ptolemaictetradrachms (13.5 ± 1 g of 25% silver).
There are 31.1035 grams per troy ounce. A spot valuation of $17.06/oz (The closing price on Monday, December 12, 2016), 30 "pieces of silver" would be worth between $185 and $216 in present-day value (USD).
The Tyrian shekel weighed four Athenian drachmas, about 14 grams, more than earlier 11-gram Israeli shekels, but was regarded as the equivalent for religious duties at that time.
Because Roman coinage was only 80% silver, the purer (94% or more) Tyrian shekels were required to pay the temple tax in Jerusalem. The money changers referenced in Matthew 21:12 exchanged Tyrian shekels for common Roman currency.
12 “And Jesus went into the temple of God, and cast out all them that sold and bought in the temple, and overthrew the tables of the moneychangers, and the seats of them that sold doves”