My girlfriend is at the airport. I am at home. Collecting her would require forty minutes of driving, and I have decided that this is a poor use of my evening.
\nHer principal objection is that we have been together for three years. She has also mentioned the time she collected me after dental surgery and several other occasions on which she incurred costs for my benefit. I do not dispute the history. I dispute its relevance to the decision currently available to me.
\nThose hours cannot be recovered. Driving to Terminal B will not return her Tuesday afternoon in March, any more than buying additional shares in a failing company recovers the original investment. A relationship can contain a great deal of past generosity without every subsequent request becoming a profitable opportunity to add more.
\nThe appropriate comparison is between the future in which I go and the future in which she takes a taxi. In both, she arrives at our apartment. In the second, I retain forty minutes and she incurs a fare. There may be additional benefits to my personal attendance, but “after everything I've done for you” is not an estimate of them.
\nIt is true that I agreed to collect her. Commitments can improve coordination, and she apparently relied on this one when deciding not to book a car. But the booking window has now passed. Keeping my promise cannot restore her earlier alternatives; it can only impose an additional cost on me. We should be evaluating whether that cost is justified from this point forward.
\nThe strongest objection concerns future trust. If I fail to appear, she may become less willing to rely on me. That belongs in the calculation. However, its magnitude depends on what she learns. Updating from “he declined an inefficient airport trip” to “he does not care about me” would be an extremely broad inference from a narrow observation. I am reluctant to subsidize that inference by driving.
\nShe has since said that she is reconsidering the relationship. This changes my estimate of its continuation value. A partner who makes three years of shared life conditional on forty minutes of driving is attaching a remarkably high price to a small transport benefit. The threatened loss therefore provides some evidence that I was overvaluing our future cooperation.
\nI understand that she sees the same history as a reason to come. I see it as something that remains true whether or not I start the car. If the prospective case for collecting her were strong, it would not require repeated appeals to an investment neither of us can recover.
\n","excerpt":"My girlfriend is at the airport. I am at home. Collecting her would require forty minutes of driving, and I have decided that this is a poor use of my evening.","tags":["Decision Theory","Relationships","Sunk Costs"],"score":365,"displayOrder":460,"thumbnail":"/assets/articles/sunk-cost-leaving-you-at-airport-thumb.webp","image":"/assets/articles/sunk-cost-leaving-you-at-airport.webp","commentCount":12,"date":"2026-08-20T00:00:00.000Z","updatedAt":"2026-09-22T00:00:00.000Z","revision":20,"status":"published"},"comments":[{"id":"seed-sunk-cost-leaving-you-at-airport-3","author":"repeated_game_theory","text":"Her past rides are the history of a repeated game, and the history tells you the terms you've both been playing on. Defecting now changes what she expects from every future round, so the past is informative about the future even though you can't recover it. The sunk-cost argument applies when the past has no bearing on what happens next. That's true of a share price and not of a person who remembers how you've treated her.","parentId":null,"score":109,"date":"2026-08-20T01:00:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-5","author":"promises_are_not_forecasts","text":"The commitments paragraph has it backwards. The value of a commitment comes from it being kept when keeping it is locally costly. A promise you'll keep only while it's still efficient to keep is a forecast.","parentId":null,"score":88,"date":"2026-08-20T01:30:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-0","author":"expected_value_bf","text":"That's the future-trust term, which is in the post. I just think its magnitude depends on what she infers, and she's inferring too much.","parentId":"seed-sunk-cost-leaving-you-at-airport-3","score":31,"date":"2026-08-20T02:00:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-1","author":"expected_value_bf","text":"I'd describe what I gave her at the time as a forecast. She interpreted it as a promise, which is part of what we're now working through.","parentId":"seed-sunk-cost-leaving-you-at-airport-5","score":26,"date":"2026-08-20T02:20:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-6","author":"not_the_lid","text":"I took a rideshare. It was $64, which I invoiced him for and he paid, which I'm told is a transfer that leaves us both better off.","parentId":null,"score":71,"date":"2026-08-20T02:40:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-4","author":"repeated_game_theory","text":"In a repeated game she's inferring exactly the right amount. You've told her the policy you'll play whenever it costs you forty minutes.","parentId":"seed-sunk-cost-leaving-you-at-airport-0","score":57,"date":"2026-08-20T02:50:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-7","author":"expected_value_bf","text":"It is, and it's also why the second future in the post is the efficient one.","parentId":"seed-sunk-cost-leaving-you-at-airport-6","score":19,"date":"2026-08-20T03:20:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-8","author":"updated_the_wrong_way","text":"The last paragraph updates in the wrong direction. Someone who'd reconsider three years over forty minutes is someone for whom the forty minutes meant something about the three years. Her reaction is evidence the continuation value was high. You read it as evidence it was low.","parentId":null,"score":64,"date":"2026-08-20T04:00:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-2","author":"expected_value_bf","text":"A high value that can be withdrawn over forty minutes isn't a stable one. Stability is part of the valuation.","parentId":"seed-sunk-cost-leaving-you-at-airport-8","score":18,"date":"2026-08-20T05:00:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-9","author":"no_pickups_since_2021","text":"I've had a standing policy since 2021 that I don't do airport pickups and nobody does them for me. Symmetric, no sunk costs, no ambiguity about promises. I'm single now, but I don't think that's related.","parentId":null,"score":47,"date":"2026-08-20T06:00:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-10","author":"terminal_b_regular","text":"Practical note. At that hour the taxi line at most terminals is thirty minutes or more, so her side of the comparison is a fare plus a wait, after a flight. Your forty minutes is closer to her total cost than the post makes it sound.","parentId":null,"score":33,"date":"2026-08-20T08:00:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false},{"id":"seed-sunk-cost-leaving-you-at-airport-11","author":"sigma_grindset_99","text":"left her on read but in real life","parentId":null,"score":-11,"date":"2026-08-21T00:00:00.000Z","own":false,"moderatable":false,"seed":true,"ownerAuthor":false}]}