AI工具订阅制还是按量付费：写个脚本算清楚

def compare_plans(monthly_quota_tokens: int,
                  subscription_price: float,
                  input_price_per_m: float,   # 每百万输入token价格（元）
                  output_price_per_m: float,  # 每百万输出token价格（元）
                  io_ratio: float = 3.0):     # 输入/输出token比例，对话类通常3:1左右
    output_tokens = monthly_quota_tokens / (io_ratio + 1)
    input_tokens = monthly_quota_tokens - output_tokens
    api_cost = (input_tokens / 1e6 * input_price_per_m
                + output_tokens / 1e6 * output_price_per_m)
    return {
        "订阅制": subscription_price,
        "按量付费": round(api_cost, 2),
        "更划算": "订阅制" if subscription_price < api_cost else "按量付费",
    }

# 示例：每月消耗500万token，订阅价99元，输入2元/百万，输出8元/百万
print(compare_plans(5_000_000, 99, 2, 8))
# {'订阅制': 99, '按量付费': 9.33, '更划算': '按量付费'}

def estimate_monthly_tokens(task_input_chars: int, task_output_chars: int,
                            tasks_per_day: int) -> int:
    # 中文场景粗略按1.5字符≈1 token估算
    tokens_per_task = (task_input_chars + task_output_chars) / 1.5
    return int(tokens_per_task * tasks_per_day * 30)

# 示例：每天20次文案任务，每次输入约2000字、输出约800字
print(estimate_monthly_tokens(2000, 800, 20))  # 约112万token/月

def break_even(subscription_price, input_price_per_m, output_price_per_m, io_ratio=3.0):
    # 反推：多少月用量时两种方式成本相等
    lo, hi = 0, 10**9
    while hi - lo > 1000:
        mid = (lo + hi) // 2
        r = compare_plans(mid, subscription_price, input_price_per_m, output_price_per_m, io_ratio)
        if r["按量付费"] < subscription_price:
            lo = mid
        else:
            hi = mid
    return lo

print(f"临界用量约 {break_even(99, 2, 8)/1e6:.1f} 百万token/月")