def prompt_cost(model_type: str, num_prompt_tokens: float, num_completion_tokens: float):
    input_cost_map = {
        "gpt-3.5-turbo": 0.0015,
        "gpt-3.5-turbo-16k": 0.003,
        "gpt-3.5-turbo-0613": 0.0015,
        "gpt-3.5-turbo-16k-0613": 0.003,
        "gpt-4": 0.03,
        "gpt-4-0613": 0.03,
        "gpt-4-32k": 0.06,
    }

    output_cost_map = {
        "gpt-3.5-turbo": 0.002,
        "gpt-3.5-turbo-16k": 0.004,
        "gpt-3.5-turbo-0613": 0.002,
        "gpt-3.5-turbo-16k-0613": 0.004,
        "gpt-4": 0.06,
        "gpt-4-0613": 0.06,
        "gpt-4-32k": 0.12,
    }

    if model_type not in input_cost_map or model_type not in output_cost_map:
        return -1

    return num_prompt_tokens * input_cost_map[model_type] / 1000.0 + num_completion_tokens * output_cost_map[model_type] / 1000.0