Basically two men talking about which is more cruel--a death sentence or life imprisonment. So, they made a bet.
One of them, the younger, would be "imprisoned" in one of the older, richer man's properties / houses. The deal was for several years (or was it decades?).
Through the years the improsoned man read books and bettered himself, while the rich man continued on with his life.
When the time was near to release the imprisoned man, the rich man was getting nervous. His wealth wasn't as great as before and (I believe) he would have to pay the imprisoned man a great deal.
However, just before his release, the imprisoned man "escaped" and left a note saying he didn't have to be paid. He has gained a lot of wisdom and this was a lot more than what money can bring.
Does anyone know the title of this short story? I would like to read it again, if anyone can tell me what it is.