If they price it like cheap insurance, they will make a lot of money and offer a worthwhile service. Pay them a low monthly rate (X) to have the service active

If they price it like cheap insurance, they will make a lot of money and offer a worthwhile service. Pay them a low monthly rate (X) to have the service active and then pay hourly at Y rate during an attack. You can play with X and Y to maximize your monthly revenue while still offering a cheap (but very valuable) service that retains your customers.