Sunk cost
What you already spent is gone whichever way you choose, so it can't help you choose. Learn to judge the future on its own, and to stop or continue for reasons that are still ahead of you.
WHY THIS MATTERS
The hole you keep digging
You've paid for the course, and it's dull. You've spent eight months on the shop, and it barely breaks even. You've queued for twenty minutes. In each case a voice says 'I can't stop now, look how much I've put in.' That sentence has cost more people more money and more years than almost any other in this course.
Notice it isn't laziness or bad maths. It's a person trying very hard to protect something that is already spent.
Sunk cost
Money, time or effort you have already spent and cannot get back, whatever you choose next. Because it is the same either way, it carries no information about which way to go. Treating it as a reason to continue is what economists call the sunk cost fallacy.
The ticket is bought. Staying in the cinema doesn't return the money, and leaving doesn't spend it twice. The only live question is how you'd rather use the next ninety minutes.
Amir's old car: keep repairing, or sell?
Spent on repairs in the last year: 1,200 <- gone whatever he decides
The mechanic's new quote: 900
What the car is worth after it: 6,000
How long it should then run: about a year
A dependable replacement costs: 14,000
Wrong question: "I've already put 1,200 in, I can't stop now."
Right question: "From today, what does 900 buy me?"900 buys about a year of driving he'd otherwise pay 14,000 for.
He repairs it, and the 1,200 played no part in that.
If the quote had been 7,000, the same 1,200 would still be irrelevant, and he'd sell.The numbers are only an example. Notice the past total appeared in the decision twice and changed nothing either time. Sunk cost doesn't mean 'quit'; it means the past can't vote.
Check yourself
Nazanin paid in advance for a six-month photography course. Two months in, she doesn't enjoy it and it isn't taking her anywhere. The fee can't be refunded. What actually decides this?
- She should finish, or the money she paid is wasted
- She should stop only if she can sell her place to someone else
- She should finish, because people who quit halfway never build anything worth having
- The money is gone either way: are four more months worth three evenings a week?
Show the answer
The money is gone either way: are four more months worth three evenings a week?
Yes. The fee is identical whether she goes or not, so it can't tip the decision. What's live is the time ahead of her and what else it could buy.
Two questions, only one of them useful
What have I put in?
Backward-looking. Feels like loyalty and seriousness. The number only ever grows, so this question can only ever say carry on, which is why it has trapped so many people in the wrong shop, job and city.
What do I get from here?
Forward-looking. Compares the cost and payoff of continuing against the cost and payoff of stopping, counted from today. Sometimes it says stop. Often it says carry on, and then you carry on for a reason that's actually true.
Four moves that get you out
- Write down what's already gone, then cross it out
The money, the months, the effort. Seeing the number is fine. Crossing it out makes the point: it is the same in both futures, so it cannot choose between them.
- Ask the stranger's question
If a friend described this exact situation today, with nothing yet spent, would you tell them to start? If the answer is a clear no, you have your answer.
- Compare the two futures, not the two pasts
Continuing costs X and brings Y from today. Stopping costs A and brings B from today. Those four things are the whole decision.
- Set the exit line before the next thing
'If I have no paying customer by month six, I stop.' Drawing the line while you're calm costs nothing and saves the version of you who will be too invested to draw it.
Check yourself
Already gone, or still ahead of you?
- The course fee Nazanin paid two months ago
- The evenings the remaining classes would take
- The two years Kamran has worked at his company
- The salary he would earn there next year
- A holiday deposit that can't be refunded
- The flights for that holiday, not yet booked
Show the answer
Already gone: The course fee Nazanin paid two months ago, The two years Kamran has worked at his company, A holiday deposit that can't be refunded
Still ahead: The evenings the remaining classes would take, The salary he would earn there next year, The flights for that holiday, not yet booked
WHY IT GRIPS
Stopping means saying you were wrong
Two things pull you back in. Continuing keeps the story open, while stopping turns a maybe into a definite loss you have to look at. And there are witnesses: you told your family about the shop, your colleagues watched you start the project. Quitting feels like being wrong in public.
This is why the hardest sunk costs are never money. Three years in the wrong career are far harder to walk away from than a phone you overpaid for.
Check yourself
Mehrdad has spent a year building a small app in his evenings. Yesterday a large company released the same thing, free. He decides to keep going, because otherwise a year of work is wasted.
Show the answer
False
The year is spent in both futures and nothing he does now brings it back. The live question is what the next year buys him against a free competitor. There may be a good answer, such as a group the free version ignores, but 'otherwise it's wasted' isn't one.
Check yourself
Sara has put eight months and most of her savings into the candle business. Sales now cover materials but not her time. A friend offers her a steady job starting next month. Which reasoning is sound?
- Keep going, or the eight months and the savings are lost for nothing
- Take the job: she should have seen this coming months ago and cut her losses
- Weigh what six more months would bring against what the job brings
- Keep going at least until she has earned back what she put in
Show the answer
Weigh what six more months would bring against what the job brings
Right. The savings are spent in both futures. She compares six months of the business, with what she has learned about real demand, against six months of the job. Either answer can be the correct one.
Stopping well
- Say it as a from here decision: 'given where I stand today, this is the better next step.' That is not a confession that starting was stupid.
- Name what you're taking with you. Eight months of running a shop is experience nobody can repossess.
- Give people the reason, not an apology. 'The numbers stopped working' ends the conversation faster than a defence.
- Then draw the exit line for the next thing, while you still have no skin in it.
Check yourself
Match each situation to the question that actually decides it
Show the answer
- A film you paid for and aren't enjoying, 30 minutes in → Is the next 90 minutes the best use of this evening?
- A degree you're two years into and dislike → What does a third year buy that stopping doesn't?
- A queue you've already stood in for 20 minutes → How much longer is the wait, counted from now?
- A repair bill that keeps growing → Does this repair buy more than the same money spent elsewhere?
Lesson recap
- Money, time and effort you've already spent are the same in every future, so they can't choose between futures.
- Ask what you get from here, not what you've put in. The second question can only ever say 'carry on'.
- The stranger's question cuts through it: would you tell a friend to start this today, from nothing?
- It grips because stopping means a definite loss and being wrong where people can see.
- This is not a licence to quit hard things, and real promises and penalties count as costs still ahead of you.