# Free tier abuse, priced per signup > Free tier abuse is scripted signups consuming a full allowance at maximum cost per call. One can cost what a hundred genuine trials do. URL: https://getculpa.com/free-tier-abuse Last reviewed: 2026-08-01 ## Answer Free tier abuse is scripted signups consuming a whole free allowance at the highest cost per call they can reach. A genuine trial user takes a fraction of what's granted, while a scripted one takes all of it with the longest prompts it can send. Culpa, a local-first LLM cost, margin, and forecast ledger, meters spend per signup, so the free tier carries a unit cost instead of a hope. ## Why this happens A free tier gets designed around what a curious human does with it, and a human samples. They try a few things, and most never reach the limit. An automated signup behaves nothing like that. It consumes the full allowance, uses the largest prompt the interface accepts, and picks whichever action is most expensive per call. The cost gap between those two users isn't a percentage, it's two orders of magnitude, so a small share of automated signups can dominate the whole free-tier bill. ## What this usually looks like - Free-tier spend grows faster than signups, which means cost per signup is rising. - A cluster of accounts exhausts its full allowance within minutes of creation. - Signups arrive in bursts with similar patterns and no subsequent activity. - Nobody can state the cost of a single free signup, so the tier has never been budgeted. ## Common mistakes - Granting the free allowance in calls rather than in spend. Why it hurts: Calls vary enormously in cost, so a call allowance lets an abuser pick the dearest action every time. Do instead: Grant a spend budget. It's the quantity you're actually giving away. - Letting the free tier reach your most expensive model. Why it hurts: Cost per abusive signup scales directly with the dearest model you expose, and abuse finds it fast. Do instead: Route free traffic to a small model, and make the frontier model part of what a trial converts into. - Measuring free-tier health by signup count. Why it hurts: Signups look like growth while the cost per signup rises underneath, so both numbers move the wrong way together. Do instead: Track cost per signup and cost per converted customer, and treat the first as an acquisition line item. ## Self-check - Compute total free-tier model spend divided by signups last month. That's your real cost of acquisition per signup. - Sort free accounts by spend and read the top fifty. The pattern will be obvious within a minute. - Check how quickly the fastest accounts exhausted their allowance after creation. - Confirm the allowance is denominated in spend rather than in calls or messages. - Divide free-tier spend by paying customers acquired. Compare that against your other acquisition channels. ## One genuine trial against one scripted one (illustrative) A free tier granting 50 calls, served on GPT-5.4 mini at real rates of $0.00075 per 1k input and $0.0045 output. Usage profiles and the automated share below are modelled. Genuine user, 11 calls at 3k in and 500 out: 11 x [(3 x $0.00075) + (0.5 x $0.0045)] = 11 x $0.0045 = $0.0495 Scripted user, all 50 calls at 120k in and 2k out: 50 x [(120 x $0.00075) + (2 x $0.0045)] = 50 x $0.099 = $4.95 One scripted signup costs exactly what 100 genuine ones do At 9,000 signups a month with 4% scripted: (8,640 x $0.0495) + (360 x $4.95) = $427.68 + $1,782.00 = $2,209.68 So 4% of signups produce 81% of free-tier spend Four percent of your signups are four fifths of the bill. Every growth dashboard reports 9,000 signups and a healthy month, and the cost per genuine signup is buried under the ones that were never people. ## Cost figures Every figure carries its confidence and its source. No figure on this site is provider-reported. - $0.0495 to $4.95 — modelled cost of one free signup, genuine trial against scripted, on GPT-5.4 mini [estimated] Source: Both endpoints at real GPT-5.4 mini rates per 1k tokens from the price book, effective 2026-07-02. A range because the usage profiles are modelled. - 81% — modelled share of free-tier spend produced by 4% of signups [calculated] Source: $1,782.00 divided by $2,209.68, from the teardown arithmetic. ## FAQ Q: How much does a free tier cost per signup? A: Divide free-tier model spend by signups for a full month. Most teams have never computed it, and the figure is usually higher than expected because a small share of automated accounts consume their full allowance while genuine users sample. Q: What's the best way to bound free-tier cost? A: Grant a spend budget rather than a call count, and route free traffic to a small model. Both bound the worst case directly, which a call limit doesn't, because an abuser will always choose the most expensive call available. Q: Should free-tier spend count as marketing or as cost of goods? A: Marketing, since it buys acquisition rather than serving a paying customer. Keeping it out of your customer-serving cost line stops it distorting gross margin, and putting it next to your other acquisition channels makes it comparable. ## Sources - OpenAI API pricing: https://developers.openai.com/api/docs/pricing Run the free Cost Leak Scan: https://app.getculpa.com/scan?source=pseo&slug=free-tier-abuse&cluster=problem Machine-readable index of every guide: https://getculpa.com/api/pages Human-readable index of every guide: https://getculpa.com/guides Site overview: https://app.getculpa.com/llms.txt Privacy: Culpa runs on your infrastructure. Your prompts and responses never leave it. Culpa counts calls to run your plan, and it fails open, so if it ever breaks your app keeps running.