repentance: great cost... huge value

But King David said to Ornan, "No, but I will buy them for the full price. I will not take for the LORD what is yours, nor offer burnt offerings that cost me nothing." So David paid Ornan 600 shekels of gold by weight for the site.
And David built there an altar to the LORD and presented burnt offerings and peace offerings and called on the LORD, and the LORD answered him with fire from heaven upon the altar of burnt offering.
1 Chronicles 21:24-26

David's principle of costly sacrifice was not just about giving in worship of the Lord. This was literally a deadly serious repentance on his part. He had disobeyed the Law of the Lord knowingly, against the protests of his own advisors, in an act of selfish pride. His ordering of the census of the fighting forces of Israel was a selfish act of human trust and a willful disbelief in the power of God. And God punished David's sin by afflicting the nation.

David was forced to make a choice for national disaster to strike Israel. And David chose three days of a raging pestilence at the hands of God's "destroying angel". The supernaturally led disease swept through the nation, stopping at the gates of Jerusalem as the destroying angel stood with drawn sword at the threshing floor of Ornan. It was there that David faced death eye-to-eye and offered sacrifices of repentance. And he would not repent without cost to himself.

The Lord was pleased with David's since and broken heart. He relented and ordered the destroying angel to sheath his sword. God showed his acceptance by raining down fire from heaven that consumed David's sacrifice, thus showing that peace and forgiveness were restored. God accepted what had cost David so very much.

So the principle to take from here is not so much about significant generosity (as I have often heard extrapolated from this passage). It is more about sincere repentance. When we mean business with God in sincere and real confession, repentance, and obedience, it will cost us something meaningful. And we should not regret the cost. We count it, willingly sacrifice it, find relief in restoration, and see God glorified in the renewal.