# `PhoenixKitAI.TtsPricing`
[🔗](https://github.com/BeamLabEU/phoenix_kit_ai/blob/v0.26.1/lib/phoenix_kit_ai/tts_pricing.ex#L1)

Estimated per-request cost for a completed TTS request, in US dollars
(`Request.cost`, a `Decimal`, as for chat/embeddings).

No TTS provider self-reports cost the way OpenRouter's chat completions do (there's
no `usage` object at all in an `/audio/speech` or xAI `/tts` response) — so unlike
`Completion.extract_usage/1`, this can't extract a real figure from the response. It
has to come from a hand-maintained rate table instead.

**Rates as of 2026-07-16 — verify against each provider's current pricing page
before trusting for billing-critical use.** These will drift; this table needs
periodic manual updates, same as any other hardcoded rate table. Sources:

- Mistral (`voxtral-mini-tts-2603`): $16 / 1M characters — https://mistral.ai/pricing/api/
- xAI (Grok TTS — one flat rate regardless of model, since xAI TTS has no
  per-model pricing tiers): $15.00 / 1M characters —
  https://docs.x.ai/developers/pricing (**corrected 2026-07-16**: originally
  shipped as $4.20/1M in 0.15.0, sourced from an OpenRouter resale listing rather
  than xAI's own direct-API rate — this module only ever calls xAI's own API, so
  that number was never the applicable one)
- OpenAI (`gpt-4o-mini-tts`): $0.60 / 1M input text tokens + $12 / 1M audio output
  tokens — https://developers.openai.com/api/docs/models/gpt-4o-mini-tts

Mistral and xAI bill per character, and `input_chars` is exact (`String.length/1`
on the request text), so their cost is exact given the rate is current. OpenAI bills
per token on both legs, but `/audio/speech` returns no token counts to read back —
estimating a token count from characters (further split into an input-text leg and
an audio-output leg) would compound two guesses, so this uses the commonly-cited
blended rate (~$0.015/minute of generated audio) applied to a duration estimated
from `audio_bytes` at the assumed bitrate instead — one estimate, not two. Treat it
as approximate wherever it's displayed.

# `cost`

```elixir
@spec cost(String.t(), non_neg_integer(), non_neg_integer()) :: Decimal.t() | nil
```

Estimated cost in dollars for a completed TTS request, rounded to the `cost`
column's 18 places, or `nil` if `provider` isn't in the rate table — same as
no cost being available today, not a new failure mode. `input_chars` and
`audio_bytes` are exactly what `PhoenixKitAI.speak/3` already records in the
request's metadata.

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*Consult [api-reference.md](api-reference.md) for complete listing*