the area that best describes the costs incurred while trying to achieve the goal
Requirements are not always met just by applying effort. Sometimes they involve trade-offs necessitating the acceptance of loss in another area in order to meet the requirement. The damages sustained in the process of meeting the requirement are the Cost of achieving the goal. Cost should not be confused with Consequence. Consequence is a state of things that either exists and will be vanquished by the goal or will come to exist unless the goal is achieved. In contrast, Cost builds over the course of the story all the way to the climax. Sometimes by the end of the story, the consequence of not achieving the goal is far less than the cumulative cost of achieving it. If there is a single large cost to be paid right at the moment of the climax, the Main Character may decide he has paid enough already and determine the goal is just not worth it, electing to stop trying. If there is no large cost at the end, the Main Character may decide to keep on going for an insignificant goal motivated by the thought of how much they already invested. In the words of the songwriter/singer Don McLean, "The more you pay, the more it's worth."