Payment depreciation
The sting of a payment fades over time, loosening the link between cost and use.
What it means
After money is spent, the memory of the outflow decays, so a sunk payment exerts progressively less psychological pressure on whether and how the purchased good is consumed. A cost paid long ago feels nearly free in the present, which is why advance purchases get under-used as time passes. The effect interacts with mental accounting: as the 'account' for a prepaid item is gradually written off, the consumer feels released from any obligation to use it. It matters for season tickets, prepaid services, and subscriptions, where prepayment predicts strong early use that tapers as the payment depreciates.
Examples
Theater patrons attend plays eagerly just after buying a subscription, but skip later shows once the long-ago payment has faded from mind.
A gym membership paid upfront in January drives four visits a week in February; by August the payment feels like ancient history and the card stays in the drawer.
A $300 online course bought in spring gets devoured for two weeks, then abandoned — not because it got worse, but because the cost stopped hurting and no longer demands justifying.
First described in Gourville & Soman (1998).