Docs answer "what will this cost me" with a real number

Eric's clean run put a price on the pipeline's only paid step:
65 shelf photos, 136 games, under a dollar on the default model. The
README's vision requirement and the guide's config section both now
say so, plus the shape of the cost — one-time, since per-photo reads
are cached and re-runs are free — and that the BGG side costs nothing.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016jXZFSTZQKzAC8fqpWSz9g

README.md

@@ -35,7 +35,7 @@ Everything runs locally, every stage survives being killed mid-run, and all arti
 ## Requirements
 
 - Python 3.12+ and [uv](https://docs.astral.sh/uv/), on macOS, Linux, or Windows. (Development happens on macOS; Windows is untested but nothing is platform-specific. One caveat: the owner-only file permissions bggpipe sets on `.env` and browser session state are POSIX-only — on Windows, keep those files in a directory protected by your account.)
-- A vision model for extraction — an [Anthropic API key](https://console.anthropic.com/) by default, or any OpenAI-compatible endpoint including a free local [Ollama](https://ollama.com/) model.
+- A vision model for extraction — an [Anthropic API key](https://console.anthropic.com/) by default, or any OpenAI-compatible endpoint including a free local [Ollama](https://ollama.com/) model. **Cost expectation:** extracting the author's whole collection — 65 shelf photos, 136 games — cost under a dollar with the default model (Claude Sonnet), one-time. Re-runs are free: every photo's read is cached, and only new or replaced photos go back to the model.
 - A BoardGameGeek account **and a registered BGG application** — as of BGG's [2025 API policy](https://boardgamegeek.com/using_the_xml_api), the XML API requires a Bearer token from a registered app. Register a free non-commercial application at [boardgamegeek.com/applications](https://boardgamegeek.com/applications) (approval can take a week or more, so **apply on day one**), then create a token. Each user needs their own; tokens must not be shared. ([You can start before it arrives.](docs/guide.md#running-before-your-bgg-token-arrives))
 
 ### Why it asks for your BGG password — and where your credentials go

docs/guide.md

@@ -32,6 +32,8 @@ Your credentials never leave your machine except to sign in to boardgamegeek.com
 
 Non-secret knobs live in `config.toml`: `photos_dir`, `data_dir`, the BGG rate limit, and the vision setup — a `[vision.<provider>]` block per provider ("anthropic" or any OpenAI-compatible endpoint, including a local [Ollama](https://ollama.com/)), with `vision_provider` picking one. Local models read spines noticeably worse than frontier ones — expect a longer proofread pass on the Titles page, not a broken pipeline.
 
+**What extraction costs:** the vision call is the pipeline's only paid step, and it's small — the author's full collection (65 shelf photos, 136 games) came to under a dollar on the default model (Claude Sonnet). It's also one-time: raw reads are cached per photo, so re-running extract is free, and only new or replaced photos are ever sent again. Everything BGG-side is free (the API token costs nothing).
+
 ## The web app
 
 ```sh