What lesson do you think Bill and the narrator learn from their encounter with red chief?

The lesson learned by Bill and narrator is best expressed by phrase "Crime does not pay."

Bill and narrator Sam learn that kidnapping is neither beneficial to their health not financially lucrative.

Explanation:

"The Ransom of Red Chief" (1907) is O. Henry's (1862-1910) comedy short story.

Initially when Bill and Sam decide to kidnap a child of wealthy parents, their aim was to easily get hold of large amount of money as ransom. They kidnap Johnny Dorset son of a wealthy banker. The boy happens to be very hyperactive and wants to be called as "red chief" from now on. When offered a candy he throws a brick at them that catches Bill right on his eye. At one time he was about to scalp Sam with a knife. He makes so much noise at night that neither Bill nor Sam can sleep.

First they reduce the ransom amount by five hundred dollars to get rid of the boy as soon as possible. But finally they have to pay Ebenezer Dorset (Johny's father) to save themselves from the boy.