If you're running Nexus with a self-connected Claude API key and using it seriously — multiple sessions, automation, daily research, coding — you've probably already felt the sting. Your Anthropic invoice at the end of the month doesn't match what you thought you were spending. And then it does. And it's more than you expected. This post is about that gap: between what you think Claude API costs and what it actually costs once you're a power user. And then about what we found instead. First, Let's Talk About the Token Math Claude Sonnet 4 (claude-sonnet-4-5 or the latest) is priced at roughly $3 per million input tokens and $15 per million output tokens on the Anthropic API as of mid-2026. Sounds cheap. It isn't, at scale.…