Based on it, it seems like Anthropic is 60% of OpenAI API-revenue wise, but just 4% B2C-revenue wise. Though I expect this is partly because the Claude web UI makes 3.5 available for free, and there's not that much reason to upgrade if you're not using it frequently.
[0]: https://www.tanayj.com/p/openai-and-anthropic-revenue-breakd...