The "insane price" would probably be if you didn't activate the transponder in the car and Hertz was charged directly and then they passed on the cost to you plus a hefty "convenience" fee. It probably would have been far cheaper to just use the provided transponder.

Then again, we've found that in a lot of these cases, the vehicle's license plate is registered to the toll transponder, so even if you had it closed, it's very possible that the tolls will get charged to the transponder account and passes along to you. There's a good chance you'll see a separate charge for tolls on your credit card in 7-10 days.