How I Cut My Claude API Bill from $340 to $67/Month (Free Interactive Workbook)

babalooz — Tue, 26 May 2026 19:55:13 +0000

My Claude API bill hit $340 last month.

Not because I was doing anything wrong — I was just building something that scales, and the costs were scaling with it.

I spent a few weeks auditing every single API call. What I found was embarrassingly fixable: about 75% of my costs came from three patterns I kept repeating without realizing it.

The 3 patterns eating my budget

1. Sending the same context on every call

I had a ~2,000 token system prompt going out with every request. No caching. Pure waste.

Fix: prompt caching. Two lines of code. Cut 40% of the bill overnight.

2. Using Sonnet where Haiku was more than enough

Classification tasks. Simple extraction. Routing decisions. All running on Sonnet.

Fix: model routing logic. Haiku costs ~20x less for tasks that don't need reasoning depth.

3. Measuring tokens instead of cost-per-task

I was watching token counts but had no idea what each feature actually cost end-to-end.

Fix: instrument cost-per-task. Immediately obvious where the leaks are.

What I built

I turned this process into an interactive workbook: 5 modules, runs in the browser, no login, no install.

Each module has an actual exercise you run against your own API key — so you see the token diff in real time, not just in theory.

grimoire-tome-1.vercel.app

It's free. Pay what you want if you find it useful.

Results

My bill went from $340 → $67/month. Your mileage will vary depending on your use case, but the patterns are consistent across most Claude API setups.

Curious what optimizations others have found — drop them in the comments.

DEV Community: babalooz

How I Cut My Claude API Bill from $340 to $67/Month (Free Interactive Workbook)

The 3 patterns eating my budget

What I built

Results