Why are costs important in economics?

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Costs are important in economics in determining the allocation of resources based on what firms are willing to pay, which in turn depends on how much consumers are willing to pay for the products produced by these resources. Costs reflect the market prices of the resources used in production, but also economic costs include the opportunity cost of using some resources that may not have an explicit market price. Economists argue that the opportunity cost of all resources should be considered when determining the real cost of production.