If you choose to self-insure, that only lowers your true cost by whatever the insurance company's profit margin is, not by the full amount of the payment. You

If you choose to self-insure, that only lowers your true cost by whatever the insurance company's profit margin is, not by the full amount of the payment. You might come out ahead, you might come out behind, but the risk of losing the car is still, on average, costing you something.