The cost of a Toll Violation depends on the number of axles on the vehicle and the state you're in.
For example if you go through a Kansas Turnpike Toll and do not pay then the violation will be a flat fee depending on the number of axles.
The fee is usually not very expensive and and if you do go through a Toll without paying you won't get pulled over by police.
But instead you just keep going and a bill will be mailed to your address.
Then you pay the toll violation and if it's your first toll violation you can usually just pay the missed toll and not get a violation bill.
Never back up or try to pay the toll if you pass through it accidentally as it's dangerous and can get you killed.
Just keep going and then pay the toll violation or toll when you get it in the mail.
Here's the information from Kansas Turnpike about Toll Violations.
Violations rate: Whether intentional or not, if a driver exits the Kansas Turnpike using an electronic lane without a valid compatible transponder, the “missed toll” is considered a violation, per Kansas statute, and will be charged the violation rate.
The violation rate is a flat fee per exit depending on the number of axles on the vehicle.
Drivers should use the cash lane or a valid compatible transponder to avoid paying this higher fare.
This rate also applies to Exit 53A tolls that are not paid on the first invoice.