The phrase a dime a dozen refers to something very plentiful, common, and therefore, inexpensive. A dime is a unit of U.S. currency that is one tenth of a dollar, or ten cents. The dime was first minted in 1796. In the 1800s, many goods such as eggs or apples were advertised to cost a dime a dozen in the United States.

What does dime in a dozen mean?

So plentiful as to be valueless. For example, Don't bother to buy one of these—they're a dime a dozen. The dime was declared the American ten-cent coin in 1786 by the Continental Congress. [

Is dime a dozen an insult?

“Dime a dozen” origins

Over time, the idiom evolved to mean the opposite. Instead of something being a good deal, it became a phrase to describe something that's not valuable and easily available.