Is costs an idiom?

"Costs" is not an idiom. An idiom is a phrase with a figurative meaning that is different from the literal meaning of the words.

"Costs" is a noun that simply refers to the amount of money that is needed to pay for something.

Here are some examples of idioms:

* Kick the bucket: To die

* Spill the beans: To reveal a secret

* Once in a blue moon: Very rarely

Let me know if you have any other words or phrases you'd like to check!