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 dirt cheap
Very inexpensive, as in Their house was a real bargain, dirt cheap. Although the idea dates back to ancient times, the precise expression, literally meaning “as cheap as dirt,” replaced the now obsolete dog cheap.
[ Early 1800s