Claude API prices, and the Sonnet 5 increase that did not happen
Claude API prices per million tokens are $5 input and $25 output for Opus 5, $2 and $10 for Sonnet 5, and $1 and $5 for Haiku 4.5[1]. Fable 5.1 sits above them all at $10 and $50, which is what Fable 5 cost before it and still costs[1].
The $2 / $10 on Sonnet 5 was announced as introductory pricing through 31 August 2026[1]. The increase to $3 / $15 scheduled for 1 September was called off, and those numbers are now the standard price[1].
Prompt caching is priced as a multiplier on the input rate: 1.25x to write a 5 minute cache, 2x for a 1 hour cache, and 0.1x to read either one[1]. Fable 5.1 and Mythos 5.1 are the exception on the read, at 0.025x[1]. A 5 minute cache pays for itself after one read, a 1 hour cache after two[1]. The Batch API halves both input and output, and stacks with the cache multipliers[1].
One thing to watch when comparing generations: models from Claude 4.7 onward use a newer tokenizer that produces roughly 30 percent more tokens for the same text[1]. A lower per-token price does not carry straight over to a lower bill.