Separate the next decision from money already spent

Separate the next decision from money already spent

Start with the question

Should an unrecoverable fee determine the next unit?

Inspect the teaching record

A fictional stall paid a nonrefundable 30-credit booking fee. One additional meal earns 8 credits and costs 5 in ingredients and labor. Up to ten additional meals can be sold under the stated conditions.

This is fictional teaching evidence. It is not an observation about an actual community or economy.

Explain the mechanism

A sunk cost cannot be recovered by the current decision. Marginal analysis compares the additional benefit and additional avoidable cost. Fixed does not always mean sunk: a future lease can sometimes be canceled. A positive contribution can reduce a loss without making the whole project profitable.

Follow the worked example

Each meal adds 8 − 5 = 3 credits before the sunk fee. Selling five yields 15 contribution and total profit 15 − 30 = −15. Closing yields −30, so five meals improve the outcome despite a loss.

Challenge the first explanation

A second location refunds its booking fee if the stall closes now. That refundable amount is avoidable and must not be treated as sunk. The first location has no such refund.

Make and revise your evidence

Write separate total-profit and incremental-decision tables for zero and five meals. Explain why the refundable location needs a different comparison.

Revise your answer to “Should an unrecoverable fee determine the next unit?” using both source IDs. Separate the checked calculation from a judgment, and identify evidence that could reverse your judgment.

Name the idea

Sunk cost: A past cost that the current choice cannot recover.

Assumption: A condition accepted for a model or argument; it needs justification before applying the result elsewhere.

Extend the investigation

Independently extend the investigation “Separate the next decision from money already spent” with a documented real dataset or scholarly source. Preserve definitions, recreate one calculation or evidence table, compare a rival explanation and report why the teaching example cannot establish the real-world conclusion.