The Model Price Index — Methodology
A single, transparent number for the cost of frontier intelligence — and exactly how it's built.
The level is computed fresh on every build from verified prices. The historical trend fills in as price history accrues — see History & honesty.
What it measures
The Model Price Index (MPI) is the equal-weighted average blended cost per million tokens across a fixed basket of frontier-flagship language models — one current, general-purpose flagship from each major lab. It answers one question in a single number: what does it cost to run a million tokens through today's best models?
It exists so the cost of frontier AI can be quoted — the way the Consumer Price Index or a stock index lets a whole market be referenced with one figure. A 156-row table can't travel into an article, a tweet, or an AI answer; one named number can.
The basket
Constituents are fixed and explicit so the index is stable and auditable — it changes only when we deliberately rebalance (see below), never silently. Today's basket:
| Model | Provider | Input /Mtok | Output /Mtok | Blended /Mtok | Weights |
|---|---|---|---|---|---|
| GPT-5.5 | OpenAI | $5.00 | $30.00 | $11.25 | Closed |
| Claude Opus 4.8 | Anthropic | $5.00 | $25.00 | $10.00 | Closed |
| Gemini 3.1 Pro | $2.00 | $12.00 | $4.50 | Closed | |
| Grok 4 | xAI | $3.00 | $15.00 | $6.00 | Closed |
| DeepSeek V4 Pro | DeepSeek | $0.435 | $0.870 | $0.544 | Closed |
| Qwen3-Max | Alibaba | $1.20 | $6.00 | $2.40 | Closed |
| Mistral Large 3 | Mistral | $0.500 | $1.50 | $0.750 | Closed |
| GLM-5.2 | Z.AI | $1.40 | $4.40 | $2.15 | Open |
Weighting & the 3:1 blend
Equal-weight. Every constituent counts the same. This is the most transparent and least gameable choice — we don't have reliable, neutral usage data to weight by popularity, and inventing weights would invite bias. Equal-weight means the index reflects the price landscape, not our guess at market share.
Blended 3:1 input:output. Output tokens cost more than input tokens, so a single "price" needs an assumed mix. A typical request reads far more than it writes (a prompt plus context, then a shorter answer), so we weight input 3× output:
blended = (3 × input + 1 × output) ÷ 4
This assumption is held constant across every model and every date, so it never distorts comparisons or the trend.
Sub-indices
The headline is one number; these cut it three ways that each tell a different story:
- Cheapest frontier token — the lowest blended cost in the basket: $0.544/Mtok (DeepSeek V4 Pro). How little frontier-class capability can cost.
- Cost per intelligence point — blended cost ÷ average benchmark score, averaged across the basket: $0.068 per point (coverage 8/8); best value: DeepSeek V4 Pro. Price adjusted for quality.
- Open vs closed spread — closed-weights flagships average $5.06/Mtok vs open-weights $2.15/Mtok — a spread of $2.91. The premium for proprietary models.
History & honesty
The trend is computed from recorded price history: every dated point uses each constituent's price at or before that date. The index has moved 0% between Jun 27, 2026 and Jun 30, 2026.
Every price in the index is a fact sourced from an official provider page and re-verified on our normal refresh cycle. The index is recomputed on every build, so the level is never stale.
Rebalancing
The basket changes only by deliberate decision — when a lab ships a new flagship that supersedes its current constituent, or a constituent is retired. Rebalances are logged here. We do not add or drop models to move the number.
Use the data
Every constituent has its own model page with verified pricing and the official source link. The full dataset is free and CORS-open at the API. Cite the Model Price Index freely — attribution to modelpricewatch.com is appreciated.