Here is a scenario that is becoming uncomfortably familiar in tech companies right now: an employee spins up an AI automation without clearing it with finance, the script runs overnight, and the invoice arrives like a cold shower the next morning. That is exactly what happened when someone ran an unapproved automation using OpenAI’s GPT-5.5 Pro, and the resulting bill was the kind that prompts an emergency Slack thread.
The numbers behind the sticker shock
OpenAI launched GPT-5.5 and GPT-5.5 Pro on April 23, 2026, positioning both models as upgrades built for complex reasoning and agent-based workflows. Standard GPT-5.5 API access runs at $5 per one million input tokens and $30 per one million output tokens. Those numbers already represent roughly double the output cost compared to earlier releases in the GPT family. The Pro variant pushes that further: $30 per one million input tokens and $180 per one million output tokens.
Output tokens are the expensive side of any API call. Every word, every line of code, every structured JSON blob the model writes back to your application is an output token. Agentic workflows, the kind designed to autonomously complete multi-step tasks like writing and debugging code, generate a lot of output. A session that runs for several hours without a human checking in can produce output volumes that, at $180 per million tokens, add up faster than most engineers mentally budget for.
