Copy-posting a post by u/lacedaimon:

Ancient numismatist here. The silver pieces referred to in the New Testament is one we call "the shekel of Tyre". As mentioned by someone else here, it had a value of 4 drachms, or what's called a tetradrachm. A drachma was a soldiers daily wage, and would be approximately $50 to $60 in today's money. So we can estimate that each tetradrachm is about $200, and so we're looking at about $6000 (though this is a pretty rough estimate), it's close. I have owned a number of them, this is what they look like: http://imgur.com/CH9CIVi

So 30 pieces of silver is equivalent of 120 days' (4 months) wages of a soldier. Nothing to sneeze at, I suppose, especially if Judas was given a pardon as well (associating with an insurrectionist?).

You might also check these previous threads:

• https://www.reddit.com/r/AskHistorians/comments/2b7ijk/judas_iscariot_purportedly_betrayed_christ_for_30/?, in which /u/talondearg points out that no denomination is mentioned

• https://www.reddit.com/r/AskHistorians/comments/1llyf7/about_how_much_in_todays_money_was_30_pieces_of/?, in which /u/lacedaimon says it's about $6000 for thirty pieces, but uses a different estimation method than /u/brojangles (day's pay vs. price of silver)

The Bible itself says he (or the priests) bought a field with the silver. Not that I am arguing for the Bible as a pure source, but it seems like the authors would have a fairly realistic view of prices. Acts 1:16-18 Matthew 27: 5-7.

Is there any validity to that sum being the equivalent of the purchasing price of a slave?