Fraud risk is higher, which means the cost of insurance is higher. I think this cost actually goes up more than just proportionally, too. Criminals will prefer

Fraud risk is higher, which means the cost of insurance is higher. I think this cost actually goes up more than just proportionally, too. Criminals will preferentially target higher value accounts, and they’ll make off with more when they do, so the risk increases more than linearly. In any case, not all costs are fixed.