This is a great example. You expect to pay for the "maintenance of the road", but what about the ongoing opportunity cost of the road and all the externalities of the road? What about all the roads that do not have tolls on them? The toll road does not exist in a vacuum, and life is not so simple so as to be able to sequester all costs into separate line items.

In fact, one of the main uses for tolls is not for the maintenance of the toll, it is for managing congestion of the road, since the road has a carrying capacity. After a certain number of vehicles, the road becomes less and less useful, so a variable rate toll can ensure a limited number of vehicles operate on the road at peak congestion.

It is simply not feasible to tie revenue to expenses 1 to 1, and specific taxes (like tolls) legislated to do that for government expenses hamstrings leaders because it removes flexibility needed to move resources around (which obviously could be used for bad, but also good, as you demonstrated your business's example).