How is “a dime a dozen” used?

In Toy Story 3 (2010), one line is: “They're a dime a dozen.”

Which movie is “a dime a dozen” from?

The clip at the top of this page is from Toy Story 3 (2010).

They're a dime a dozen.

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very common and therefore not valuable

オックスフォード映画の 100%
very common and therefore not valuable
What good will that do, boss? Forget it. Her kind's a dime a dozen.
Phil, when are you gonna learn girls like that are a dime a dozen?

定義：Oxford Advanced Learner's Dictionary 第 9 版