​
Adding a custom cost

You can add a custom cost by using the add_cost method. The three required fields are llm_id, prompt_token_cost, and completion_token_cost. llm_id is the name of the LLM (e.g. gpt-4o). prompt_token_cost and completion_token_cost are cost per token for the LLM (if the LLM prices were specified inper million tokens, make sure to convert the value). You can also set effective_date to a datetime, to make the cost effective at a specific date, this defaults to the current date.
import weave
from datetime import datetime

client = weave.init("my_custom_cost_model")

client.add_cost(
    llm_id="your_model_name",
    prompt_token_cost=0.01,
    completion_token_cost=0.02
)

client.add_costs(
    llm_id="your_model_name",
    prompt_token_cost=10,
    completion_token_cost=20,
    # If for example I want to raise the price of the model after a certain date
    effective_date=datetime(2025, 4, 22),
)

​
Querying for costs

You can query for costs by using the query_costs method. There are a few ways to query for costs, you can pass in a singular cost id, or a list of LLM model names.
import weave

client = weave.init("my_custom_cost_model")

costs = client.query_costs(llm_ids=["your_model_name"])

cost = client.query_costs(costs[0].id)

​
Purging a custom cost

You can purge a custom cost by using the purge_costs method. You pass in a list of cost ids, and the costs with those ids are purged.
import weave

client = weave.init("my_custom_cost_model")

costs = client.query_costs(llm_ids=["your_model_name"])
client.purge_costs([cost.id for cost in costs])

​
Calculating costs for a Project

You can calculate costs for a project by using our calls_query and adding include_costs=True with a little bit of setup.
import weave

weave.init("project_costs")
@weave.op()
def get_costs_for_project(project_name: str):
    total_cost = 0
    requests = 0

    client = weave.init(project_name)
    # Fetch all the calls in the project
    calls = list(
        client.get_calls(filter={"trace_roots_only": True}, include_costs=True)
    )

    for call in calls:
        # If the call has costs, we add them to the total cost
        if call.summary["weave"] is not None and call.summary["weave"].get("costs", None) is not None:
            for k, cost in call.summary["weave"]["costs"].items():
                requests += cost["requests"]
                total_cost += cost["prompt_tokens_total_cost"]
                total_cost += cost["completion_tokens_total_cost"]

    # We return the total cost, requests, and calls
    return {
        "total_cost": total_cost,
        "requests": requests,
        "calls": len(calls),
    }

# Since we decorated our function with @weave.op(),
# our totals are stored in weave for historic cost total calculations
get_costs_for_project("my_custom_cost_model")

​
Setting up a custom model with custom costs

Try our cookbook for a Setting up costs with a custom model or
Open In Colab
Open in Colab