Most AI app ideas look cheap in a demo and become expensive at scale. A prototype with 100 users may cost almost nothing. The same product with 10,000 active users, long chat history, large prompts and expensive models can become a serious monthly bill. This calculator estimates the real LLM cost before you build — users, calls, tokens, model choice and simple optimisations like caching or batching.
Cheapest models for this workload
Same usage, every model ranked by monthly cost.
| Model | Cost / month | Per user |
|---|
Build your AI app fast with v0 →
Referral link — v0 by Vercel turns a prompt into a working app UI. Then estimate its running cost above.
How to read this
Your AI bill is mostly users × calls × tokens × price. The biggest levers, in order: which model (small vs frontier is often 20–50× cheaper), output length (output costs 3–5× input — cap it), and input length (trim system prompts and retrieved context). Caching repeated context and batching non-urgent jobs cut more.
Picking a model? Compare them head-to-head on the AI API cost calculator, or read GPT vs Claude vs Gemini. Building RAG or a chatbot? Those have their own cost drivers (embeddings, vector DB, retrieval size) — guides coming.