Cost Models

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

Cost model types

Type	Use case	How it works
`per_unit`	Fixed cost per event	Every event costs the same (e.g. $0.03 per API call)
`per_model`	LLM token pricing	Different rates per model (GPT-4o costs more than GPT-4o-mini)
`tiered`	Volume discounts	Cost per unit changes at thresholds

Create a cost model (sk_ key required)

Per-model (recommended for LLM)

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.

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
  }'

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 }
    ]
  }'

List cost models

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

Delete a cost model

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

How it connects to margin

Once a cost model is configured, every usage event matching the metric_code is automatically enriched with cost data:

SDK sends nozle.track(customerId, "llm_tokens", { model: "gpt-4o", input_tokens: 500, output_tokens: 200 })
The margin engine looks up the cost model for llm_tokens
For per_model type: calculates (500 × 250 + 200 × 1000) / 1,000,000 = $0.000325
Stores revenue, cost, and margin in the margin events table
Dashboard shows per-customer, per-model, per-feature margin breakdown

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