Price-increase emails are designed to slip past the cognitive machinery that normally registers spending. The research that explains why the increases land without resistance.
The email arrives in your inbox on a Tuesday afternoon. The subject line says something like "Updates to your subscription" or "An important change to your account." You open it because you open most emails. The first paragraph thanks you for being a customer. The third paragraph mentions, somewhere in the middle of a longer sentence, that the monthly price is changing. You glance at it. You close the tab. The next month the new amount is on your card and you don't notice that either.
This is how subscription creep happens — the steady upward drift in what you pay for services you already had — and the mechanics aren't really about the email. They're about a much older feature of how human memory works around money.
Two papers, both more than twenty years old, do most of the explanatory work. The first is the same Soman paper that explains forgotten subscriptions: the rehearsal hypothesis. Paying by cash or check forces the consumer to write down or count the amount, which plants the payment in memory. Paying by automatic recurring billing does neither. The charge fires; the amount changes; the brain has nothing to hold onto.
Past payments strongly reduce purchase intention when the payment mechanism requires the consumer to write down the amount paid (rehearsal) and when the consumer's wealth is depleted immediately rather than with a delay (immediacy). — Soman (2001), Journal of Consumer Research
The second is a 1998 Marketing Science paper by Drazen Prelec and George Loewenstein, working at MIT and Carnegie Mellon respectively. Their concept is payment-consumption coupling — the cognitive link between using something and paying for it. Coupling is what makes a single decision out of two events. Decoupling, which credit and subscription billing produce by design, is what severs that decision into two events that never meet.
Credit mechanisms decouple the act of consumption from the act of payment… therefore weaken self-regulatory processes, enabling more spontaneous consumption. — Prelec & Loewenstein (1998), Marketing Science
A price increase, in this framework, is a perfect demonstration of both mechanisms operating together. The increase is communicated by email — typically buried inside paragraph three of a longer message, written in language designed to avoid triggering attention. There is no rehearsal because you didn't engage with the new amount. There is no coupling because the new amount doesn't show up until weeks later, against the same auto-billed line item that has been firing on the same card for months. By the time you see the new figure on your statement, your brain has nothing to compare it against. The new amount looks the same as the old amount because both look the same as every other line item that auto-deducted that month.
Industry market research bears this out. Across multiple Deloitte and Antenna surveys, the share of consumers who report being aware of recent price increases on their streaming services consistently lags the share who actually experienced one — usually by 20 to 40 percentage points. The increase happened; the consumer didn't notice; the spending continued. The pattern repeats every 12 to 18 months because that's the cadence the providers have determined produces the most revenue per subscriber with the least visible churn.
The compounding cost over time is more interesting than any single price change. A subscription that started at $7.99 in 2017 and has had three price changes at the industry-typical 8% per year now costs roughly $13.50. The household that has held it has paid, cumulatively, about $850 for that line item alone. None of those $7.99-then-$8.99-then-$10.99-then-$11.99-then-$13.50 increments registered as a decision worth thinking about. Together they cost more than a vacation.
What the research suggests as the intervention is straightforward, if not particularly easy to execute. The friction Soman identified as the source of accurate spending memory can be restored manually, simply by re-engaging with the amounts on a schedule. Quarterly is reasonable. Pull the statements; list every recurring merchant with the current price; compare against the prior list. The differences become visible the moment you write them down.
The deeper observation the research doesn't quite spell out is that this work is something the system has been designed to make you not do. The email language, the calendar timing, the absence of any single moment of explicit reconsent — none of it is accidental. The same friction Soman identified as the source of spending memory is, from the provider's perspective, an inefficiency to be removed. They have removed it. The audit is what puts it back.
The harder question, once you've done the audit, is what to actually do with the number. The answer most consumer-psychology research suggests is the one most people find counterintuitive: don't ask whether the current price is fair. Ask whether you would sign up for the service today, at this price, given the way you currently use it. The first framing trips the sunk-cost bias and tends to produce a defense of the status quo. The second framing strips out the history and asks the cleaner question. For services you would re-subscribe to today, keep paying. For the rest, the increase the provider sent you in email is the moment to stop.