How does AI pricing work for each?
Both vendors bill API usage by the token, quoted per million tokens, with **input** and **output** priced separately (output almost always costs more). A token is a chunk of text — roughly a few characters — so longer prompts and longer answers both cost more; see What is a token in AI?. Consumer subscriptions (ChatGPT Plus, Claude Pro) are flat monthly fees and a separate question from API billing, which is what this article focuses on.
Each vendor offers tiers. Anthropic's lineup spans Claude Haiku 4.5 (fast and cheap), Claude Sonnet 4.6 (balanced), and Claude Opus 4.8 (most capable). OpenAI's GPT-5 family spans lighter, lower-cost tiers up to the GPT-5.5 flagship and GPT-5.5 Pro for the hardest reasoning. The tier you choose usually changes your bill far more than the Anthropic-vs-OpenAI choice does. Confirm the current tiers on Anthropic models and OpenAI models.