From budget page
In these areas, vehicles are equipped with a transponder tag. Simply slide open the transponder box on the windshield and drive through a designated I-Pass (Chicago), EZ Pass (Northeast) or AutoExpreso (Puerto Rico)transponder based lane. When you use these lanes, the toll system identifies the car and charges the standard toll fee as published by the toll authority plus the convenience fee of $2.95 per rental day for the entire length of your rental (maximum $14.75 per month). These fees are charged directly to the credit card on file for your rental. If you do not choose to use the dedicated lanes then you must pay any toll fees independently.
Who know the T&C's are ambiguous. What is the standard toll fee