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Cost models tell Nozle what each unit of usage costs you. Without cost models, the margin engine can’t calculate your AI spend.

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Cost model types

TypeUse caseHow it works
per_unitFixed cost per eventEvery event costs the same (e.g. $0.03 per API call)
per_modelLLM token pricingDifferent rates per model (GPT-4o costs more than GPT-4o-mini)
tieredVolume discountsCost per unit changes at thresholds

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Create a cost model (sk_ key required)

curl -X POST https://api.nozle.app/api/v1/cost-models \
  -H "Authorization: Bearer sk_nozle_..." \
  -H "Content-Type: application/json" \
  -d '{
    "name": "LLM Token Pricing",
    "metric_code": "llm_tokens",
    "cost_type": "per_model",
    "model_rates": {
      "gpt-4o": { "input": 250, "output": 1000 },
      "gpt-4o-mini": { "input": 15, "output": 60 },
      "gpt-4.1": { "input": 200, "output": 800 },
      "gpt-4.1-mini": { "input": 40, "output": 160 },
      "claude-sonnet-4-20250514": { "input": 300, "output": 1500 },
      "claude-haiku-4-20250414": { "input": 80, "output": 400 }
    }
  }'
Rates are in cents per 1M tokens. The margin engine calculates cost automatically when events arrive with model, input_tokens, and output_tokens properties.

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Per-unit

curl -X POST https://api.nozle.app/api/v1/cost-models \
  -H "Authorization: Bearer sk_nozle_..." \
  -H "Content-Type: application/json" \
  -d '{
    "name": "API Call Cost",
    "metric_code": "api_calls",
    "cost_type": "per_unit",
    "amount_cents": 3
  }'

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Tiered

curl -X POST https://api.nozle.app/api/v1/cost-models \
  -H "Authorization: Bearer sk_nozle_..." \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Volume Pricing",
    "metric_code": "api_calls",
    "cost_type": "tiered",
    "tier_mode": "SLAB",
    "tiers": [
      { "up_to": 10000, "unit_amount_cents": 5, "flat_amount_cents": 0 },
      { "up_to": 100000, "unit_amount_cents": 3, "flat_amount_cents": 0 },
      { "up_to": null, "unit_amount_cents": 1, "flat_amount_cents": 0 }
    ]
  }'

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List cost models

curl https://api.nozle.app/api/v1/cost-models \
  -H "Authorization: Bearer sk_nozle_..."

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Delete a cost model

curl -X DELETE https://api.nozle.app/api/v1/cost-models/{id} \
  -H "Authorization: Bearer sk_nozle_..."

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How it connects to margin

Once a cost model is configured, every usage event matching the metric_code is automatically enriched with cost data:
  1. SDK sends nozle.track(customerId, "llm_tokens", { model: "gpt-4o", input_tokens: 500, output_tokens: 200 })
  2. The margin engine looks up the cost model for llm_tokens
  3. For per_model type: calculates (500 × 250 + 200 × 1000) / 1,000,000 = $0.000325
  4. Stores revenue, cost, and margin in the margin events table
  5. Dashboard shows per-customer, per-model, per-feature margin breakdown