dirt cheap

Very inexpensive. The idea of something being as cheap as dirt dates back at least to Roman times. Petronius’s Satyricon (A.D. 60) says, “In those days food could be had for dirt” (Illo tempore annoma pro luto erat). It may already have been a cliché by the time Dickens used it in Oliver Twist (1838): “I sold myself ... cheap, dirt cheap!”