a price on (one's) head
An amount of money being offered as a reward for one's capture, or, in some cases, killing. I'm sorry, but we can't travel with your brother any longer. The sheriff has put a price on his head and it's too dangerous for the rest of us! I'll never be able to live peacefully in this town as long as I have a price on my head.
price on one's head
A reward for capturing or killing someone, usually someone guilty of a crime. For example, He was a serial killer, and they put a price on his head. The head in this term presumably alludes to the older punishment of beheading. [Mid-1700s]