---
name: Sunk Cost
slug: sunk-cost
type: cognitive bias
status: running
version: 4.2.1
released: "prehistory"
maintainer: the part of your brain that hates waste
dependencies:
  - loss-aversion
  - ego
  - memory
  - hope (deprecated)
license: Irrevocable
tags:
  - economics
  - psychology
  - decision-making
  - self-sabotage
  - very-common
---

Sunk Cost

What it actually is

Money, time, or effort already spent that cannot be recovered, being used anyway to justify spending more.

How it works

The mechanism is elegant in how wrong it is:

Resource is committed to an outcome
Outcome begins failing
Brain registers the loss as ongoing, not complete
Additional resources are deployed to "protect" what is already gone
Those resources are also lost
Go to step 3

The core error: past expenditure is not a variable in whether a future action is worth taking. The rational agent knows this. Almost no one is a rational agent.

"I've already seen three episodes. I have to finish this season." — every user, always

Features

Works on individuals, corporations, governments, and relationships
Scales linearly with investment size
Particularly potent when the original decision was made publicly
Compatible with all major operating systems including grief and pride
Self-reinforcing: the longer it runs, the harder it is to terminate

Known bugs

Bug	Observed behavior	Status
Escalation loop	User increases investment to avoid admitting loss	Won't fix
Identity merge	User cannot separate self-worth from the sunk cost object	Open
Hindsight suppression	User retroactively upgrades original decision's quality	By design
Rational override failure	User knows the fallacy, applies it anyway	Known since forever

Error codes

ERR_CANNOT_QUIT_NOW     // "I've come too far to stop"
ERR_INVESTMENT_GRIEF    // "But I already paid for it"
ERR_NULL_EXIT_STRATEGY  // No off-ramp was ever built
WARN_IDENTITY_ENTANGLED // The cost is now the self
FATAL_DECADE_MARRIAGE   // System has been running too long to audit

Edge cases

The good-enough product: User stays with inferior software because they learned it. See also: inertia.
The degree: User takes a job they hate because the credential demanded it. The credential is real. The obligation it implies is not.
The war: Nations are not exempt. This is not a metaphor.
Sunk cost about sunk cost awareness: User has read so much behavioral economics that quitting anything feels like failure to apply their knowledge correctly.

Configuration

# sunk-cost/config.yml
trigger_threshold: low
exit_resistance: high
emotional_weight_multiplier: 1.8
rational_override: disabled
public_commitment_amplifier: true

Defaults ship as shown. Most users never open this file.

FAQ

Can I use sunk cost as a reason to continue something? No. This is exactly what the spec is warning you about.

What if I really am close to the goal? Evaluate based on remaining cost versus remaining value. The past does not vote.

Is commitment the same thing? Commitment is choosing to continue because the future looks worthwhile. Sunk cost is continuing because the past feels heavy. The outputs can look identical from the outside.

Why does knowing about this not help? Metacognition is not a patch. It is documentation. Documentation does not prevent bugs.

drafting spec…