Brilliant article on Peter Sefton`s site. Hits the nail on the head.
Matthew 26:14 Then one of the twelve, called Judas Iscariot, went unto the chief priests,
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.
16 And from that time he sought opportunity to betray him.