The cost of shelter, food, transportation, medical and all the other bills we face.
So for most the us, the value of money and the value of "earning a living" is something we can understand and appreciate.
But if we think about the cost of our eternal lives ... there was only one who could pay that debt - our Lord and Savior Jesus Christ.
1 Peter 1:18-19
"For as much as you know that you were not redeemed with corruptible things, as silver and gold … But with the precious blood of Christ, as of a lamb without blemish and without spot."