Short answer: it depends how you pay, and the difference isn't where most people think it is. On paper, Sonnet 5 looks a lot cheaper than Opus 4.8, at $2 input and $10 output per million tokens against Opus's $5 and $25 (at least until August 31, 2026). After that date Sonnet rises to $3 and $15, exactly the old Sonnet 4.6 price.
But price per token is only part of the story. An independent benchmark from Artificial Analysis took a hard reasoning task and let both models work it at maximum effort. The result: Sonnet 5 used about 69,000 output tokens, Opus 4.8 needed only about 41,000. The actual cost for the finished task came out almost identical, $1.53 against $1.80. It's like taking two taxis to the same destination: Sonnet takes the longer road at a lower per-kilometer rate, Opus drives straight at a higher rate, but by the end of the ride the fare comes out almost the same.
On our team, the choice between models comes down to how you're billed, not personal taste. Pro or Max subscribers don't even need to think about it, because the price is fixed either way: they work with Opus for everything, and switch to Sonnet only when the five-hour quota runs out or when they need speed. For anyone paying per token, through the API or an automation, the story is different: our default is Sonnet 5 at low to medium effort. Opus comes into play when the task demands complex reasoning or when our reputation is riding on the output, and at that point price is already a secondary concern.
In our workshops there's an iron rule for anyone showing up with a Pro subscription: work only with Sonnet 5 from the first minute, and don't touch Opus until you're back home. The reason is simple: the shared five-hour quota runs out much faster than it seems, and a three to four hour workshop can burn through the whole window on its own.
A prompt, on the house
Before picking a model, two questions:
1. Are you on a subscription (Pro/Max) or paying per token (API/automation)?
← Subscription: Opus by default, switch to Sonnet only when the quota runs out.
← API: Sonnet 5 at low-medium effort by default.
2. On the API, does the task need hard reasoning at maximum effort?
← Yes: Opus. At this point the cost is nearly identical, so go for quality.
Coming to a workshop on a Pro subscription? Sonnet 5 only, the whole time. Opus is for your homework.
