The Cost Surprise
First month with OpenAI: $4,000.
We didn't have controls. We didn't have monitoring.
We learned.
The Basics
Token Math
GPT-4o: $5/1M input tokens, $15/1M output.
500-word article: ~750 tokens in, ~500 tokens out.
Cost: $0.0075 per article.
1,000 articles: $7.50.
Cost Control
1. Model Selection
GPT-4o: Expensive. Powerful.
GPT-4o-mini: Cheap. Good enough for most tasks.
Use the cheapest model that works.
2. Caching
Cache repeated requests.
Same prompt twice? Only pay once.
3. Prompt Optimization
Shorter prompts = fewer tokens = cheaper.
Be concise. Remove fluff.
Best Practices
1. Monitor Usage
Set up billing alerts.
Know before you overspend.
2. Rate Limiting
Protect against runaway usage.
One user shouldn't bankrupt you.
3. Fallbacks
If API fails, what happens?
Design for graceful degradation.
The Implementation
1. Track per User
Know which users drive costs.
await trackCost(userId, promptTokens, completionTokens)
2. Set Limits
if (user.monthlyCost > 100) {
return "Upgrade required"
}
3. Use Smaller Models
For simple tasks: Use gpt-4o-mini.
For complex: Use gpt-4o.
The Honest Take
OpenAI is powerful. It's also expensive.
Design for cost. Monitor usage. Set limits.
Otherwise, you'll get a surprise bill.
