dime a dozen
So plentiful as to be valueless. For example, Don't bother to buy one of thesethey're a dime a dozen. The dime was declared the American ten-cent coin in 1786 by the Continental Congress. [First half of 1900s]
they're a dime a dozen. The dime was declared the American ten-cent coin in 1786 by the Continental Congress. [First half of 1900s]