An unconscionable price asked by a merchant: Highway robbery is no name for it/ 100 bucks? That's highway robbery!(1886+)
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with high way robbery
The exaction of an exorbitantly high price or fee. For example, You paid ten dollars for that meat? That's highway robbery. This term, used figuratively since the late 1800s, alludes to literal robbery of travelers on or near a public road.