Your benefit from attending your cousin's wedding in Chicago would be $550. The cost of a round-trip airline ticket is $500, and there are no other costs, so you bought the ticket and plan to attend the wedding. However, your cousin then postponed the wedding by a week. Your ticket is non-refundable, but the airline will let you change the date of your ticket for a fee of $100. You decline, because "the total cost of attending the wedding is now $500 + $100 = $600, which is greater than the benefit."
Which decision pitfall have you fallen into?
The pitfall of ignoring implicit costs.
The pitfall of failing to think at the margin.
The pitfall of measuring costs or benefits proportionally .
The pitfall of thinking normatively rather than positively.