The cost of a decision is also known as a(n)

The answer would be an opportunity cost

Example of opportunity cost :

Let's say an artist have 2 choices for their Friday's schedule. The first one is to do a free meet and greet with his fans. The second one is to serve as a Guest star on a tv show, in whcih he will receive a payment.

Then, the artist chose to do the meet and greet instead.

The amount of money that the artist lost from his decision, is an example of an opportunity cost

Hope this help you out