There is a great thread in here about rental cars and Route 6 charges. The way they are broken by the calendar month (June 28 to July 3 you pay for 2 months, but July 1 to July 29 you pay for 1 month, the standard engagement fee, the actual use fee and then the bill which can arrive 5 to 8 months later.
All things being equal, the road is worth the cost.