There's the cost to do productive work, and the proportion of work which is actually productive. GPT5.5 medium is ~20% the cost of Opus and 27% the cost of Son

There's the cost to do productive work, and the proportion of work which is actually productive. GPT5.5 medium is ~20% the cost of Opus and 27% the cost of Sonnet on a task by task basis. That's a material difference.