The enormity of Judas' crime is set forth
But O ungodliest of men, “you seed of Chanaan and not of Juda,” and no longer “a vessel of election,” but “a son of perdition” and death, you thought the devil's instigations would profit you better, so that, inflamed with the torch of greed, you were ablaze to gain 30 pieces of silver and saw not what riches you would lose. For even if you did not think the Lord's promises were to be believed, what reason was there for preferring so small a sum of money to what you had already received?
You were wont to command the evil spirits, to heal the sick, to receive honour with the rest of the apostles, and that you might satisfy your thirst for gain, it was open to you to steal from the box that was in your charge. But your mind, which lusted after forbidden things, was more strongly stimulated by that which was less allowed: and the amount of the price pleased you not so much as the enormity of the sin. Wherefore your wicked bargain is not so detestable merely because you counted the Lord so cheap, but because you sold Him Who was the Redeemer, yea, even yours, and had no pity on yourself. And justly was your punishment put into your own hands because none could be found more cruelly bent on your destruction than yourself.
Source: Sermons (New Advent)