Once on a family vacation to Florida, I found myself on a toll road with no toll booths. If you didn't have a toll transponder, they just took a picture of the license plate and billed you later.
I had rented the car in Georgia, so the transponder wasn't even an option. A couple of weeks later at home, I got a bill in the mail - $4 for the toll, and a $50 processing fee from the rental company. It had already been charged to my credit card.
In case this helps anyone: Most cashless toll roads have an option where you can go to a website within a couple days and pay the toll online by entering your license plate. If you do this, your rental car company shouldn't get a bill, and you will avoid paying the extra fees.
I agree that the processing fees charged by rental car companies are ridiculous, though. The per-day rental charge for toll passes (in addition to the tolls) is also ridiculously high.
This happened to me in Italy... i guess it was Avis? Not sure. They billed me 25E processing fee for providing to police my details, because apparently I got a parking ticket. Never got the ticket itself, either from Avis or from police.
The funny thing is that they managed to charge my card, although it was a debit card that had expired in the meanwhile, and the linked account had 0EUR on it (the bank gracefully paid them, then automatically converted money from my other accounts to cover for my now-negative account balance).
I had that with Europcar and asked to see the infringement notice. They said they had shredded it after telling the govt it was me driving, so they couldn't give it to me. All part of their GDPR compliance allegedly. So even consumer protection laws can be used to screw you.
The credit card being expired means nothing, you have to completely leave said bank. Direct debit arrangements are even worse in this regard (see also: gym memberships).
Yeah, with transponder fees sometimes they charge you weekly, even if you only use the transponder once. [1] In some places (e.g., the Golden Gate Bridge) there's no lane for manual payment so you pretty much have to have the transponder. I think there may be a way you can manually pay your toll online, but it's possible this has to be done in advance (and I know no one who has ever done it). Basically, you have to pay the rental car transponder fees in some places, and they're a cash cow for the rental car companies.
At the Golden Gate Bridge there's no lane for manual payment so you pretty much have to have to travel north. Make your way back via Fresno and San Jose, going clockwise around the bay.
I had rented the car in Georgia, so the transponder wasn't even an option. A couple of weeks later at home, I got a bill in the mail - $4 for the toll, and a $50 processing fee from the rental company. It had already been charged to my credit card.