An ignition interlock device is a device which can keep a car from starting if the driver has been drinking alcohol and is over the limit. The device can also do random tests for breath alcohol content. There are a few costs associated with an ignition interlock device. The offender typically must pay to have their license reinstated. Secondly, the installation for the device is usually between $50 and $200. Finally, the monthly rental fee for the device is from $50 to $100. The average cost of an ignition interlock device is roughly $250.