All this, O king, Araunah gives to the king.” And Araunah said to the king, “May the Lord your God accept you.” But the king said to Araunah, “No, but I will buy it from you for a price. I will not offer burnt offerings to the Lord my God that cost me nothing.” So David bought the threshing floor and the oxen for fifty shekels of silver. 2 Samuel 24: 23-24
The house money effect is when a spender is willing to take a greater risk when spending the profit. The term comes from the casino phrase, playing with "house money." The idea behind this effect is that house money doesn't have a high cost because it's a surplus. It doesn't cost you much because it is merely the extra money gained through a fortunate roll of the dice. In the above passage, this king refuses to play with house money.
Unless it costs something, the value is absent from payment.
King David understood the value explicitly. He was a man of such high integrity that he refused to take the easy way out. In this situation, He was presenting a sacrifice in response to his sin. Araunah was willing to give David the equivalent of house money. This man was unwilling to give to God unless it cost him something. A man after God's own heart knew that to honor God; it meant real sacrifice. To make a real sacrifice, it had to cost him something.
DO THIS TODAY: Make a costly sacrifice to God.