I think it should be an item called toll to be used as the payment point. And it should be a parameter in route to avoid this points. We could add the price of the toll and even we could know after routing the cost of our route.
the real world is a bit more complex, because the price depends on the point you enter the highway. it could be a table for each toll to select for an entry toll point the price for this exit toll…
what do you think?