Introduction
One of the most common questions from SaaS founders and developers is: how much does a chatbot actually cost per month?
The answer depends on three things: which AI model you use, how many users you have, and how often they chat. In this guide, we break it down with real numbers.
What Drives Chatbot API Costs?
AI chatbots are billed by tokens — chunks of text processed by the model. Every message your user sends (input) and every reply the bot generates (output) costs tokens.
The formula is simple:
- Monthly cost = (Input tokens + Output tokens) × Price per token × Monthly requests
Current Model Pricing (June 2026)
- GPT-4o: $2.50 input / $10.00 output per 1M tokens
- GPT-4o Mini: $0.15 input / $0.60 output per 1M tokens
- Claude Sonnet 4.6: $3.00 input / $15.00 output per 1M tokens
- Claude Haiku 4.5: $1.00 input / $5.00 output per 1M tokens
- Gemini 2.5 Pro: $2.00 input / $12.00 output per 1M tokens
- Gemini 2.5 Flash: $0.30 input / $2.50 output per 1M tokens
Real-World Cost Examples
Assumptions: 500 input tokens + 300 output tokens per message exchange.
1,000 Monthly Active Users — Daily Usage
Each user chats daily (~30 sessions/month), 4 messages per session = 120,000 requests/month.
- GPT-4o: ~$540/month
- GPT-4o Mini: ~$32/month
- Claude Sonnet 4.6: ~$720/month
- Claude Haiku 4.5: ~$216/month
- Gemini 2.5 Flash: ~$84/month
1,000 Monthly Active Users — Weekly Usage
Each user chats weekly (~4 sessions/month), 4 messages per session = 16,000 requests/month.
- GPT-4o: ~$72/month
- GPT-4o Mini: ~$4.30/month
- Claude Sonnet 4.6: ~$96/month
- Claude Haiku 4.5: ~$28.80/month
- Gemini 2.5 Flash: ~$11.20/month
10,000 Monthly Active Users — Weekly Usage
- GPT-4o: ~$720/month
- GPT-4o Mini: ~$43/month
- Claude Sonnet 4.6: ~$960/month
- Claude Haiku 4.5: ~$288/month
- Gemini 2.5 Flash: ~$112/month
Which Model Should You Choose?
Under $50/month budget: GPT-4o Mini or Gemini Flash — both deliver solid quality at a fraction of the cost.
$50–$200/month budget: GPT-4o for general use, Gemini Pro for long-context tasks.
Enterprise scale: Negotiate volume discounts directly with OpenAI, Anthropic, or Google.
Hidden Costs to Watch Out For
- System prompts: Long system prompts count as input tokens on every request
- Conversation history: Sending full chat history each turn multiplies token usage fast
- RAG / search context: Adding document context can 3-5x your input tokens
Use Our Free Calculator
Want to estimate your exact chatbot cost? Use our AI API Cost Calculator — just enter your users, frequency, and use case to get a breakdown across all major models.
Conclusion
A chatbot with 1,000 users doesn't have to cost a fortune. With GPT-4o Mini or Gemini Flash, you can run a production chatbot for under $50/month. The key is choosing the right model for your quality requirements and optimizing token usage from day one.