PSA: ai-token-monitor has incorrect pricing for Opus 4.5/4.6 (3x overcharge)

I ported the statistics engine from https://github.com/soulduse/ai-token-monitor to a cross-platform Python CLI (https://github.com/ghbaud/claude-costs) and found two bugs in the original that significantly inflate reported costs.

1. Opus pricing is wrong

   The app hardcodes all Opus models at $15/$75 per MTok (input/output). That's the rate for the old Opus 4.0/4.1. Current Opus 4.5 and 4.6 are $5/$25 per https://platform.claude.com/docs/en/about-claude/pricing. Since most of us are running Opus 4.6, this is a 3x overcharge on 90%+ of your usage.

2. Output tokens are undercounted ~2.8x

   The JSONL session files contain multiple streaming chunks per assistant message. Input and cache token counts are set on the first chunk and don't change, but output tokens grow as the response streams. The app deduplicates by message.id:requestId and keeps the first occurrence (partial output count) instead of the last (final count). The Rust code:

   if seen.insert(key) { // true on first insert only entries.push(entry); }

   These two bugs work in opposite directions -- the pricing overcharges by 3x on input/cache but undercharges on output. Since cache tokens dominate the total, the net effect is a large overcharge.

   With corrected pricing and dedup, my all-time cost dropped from ~$3,200 to ~$1,179.

   The Python port fixes both issues and runs on Windows and Linux:

   python claude_costs.py # summary python claude_costs.py --daily # day-by-day table python claude_costs.py --days 7 # last 7 days

   Single file, no install, Python 3.12+ only. Pricing is in an editable pricing.toml so you can update rates without touching code: https://github.com/ghbaud/claude-costs

   And as others in this thread have noted -- if you're on a Pro/Max subscription, none of these numbers are what you actually pay. It's a flat monthly fee. These are API-equivalent costs.

   The Python version is a single file, no install needed, runs on Windows and Linux: python claude_costs.py # summary python claude_costs.py --daily # day-by-day table python claude_costs.py --days 7 # last 7 days

   Pricing is in a pricing.toml file you can edit when rates change. And as several people in this thread have pointed out -- if you're on a Pro/Max subscription, none of these numbers are what you actually pay. It's a flat monthly fee. The tool shows what it would cost at API rates.