I currently pay a $15 round trip toll for bridges I use in the NYC area. The bridges cost a fraction of that to operate and maintain. The remainder of the toll goes to support public transit in the city. So you are right: TINSTAAFL.
It's more complex than that. If you take journeys that aren't necessary or use transportation in otherwise inefficient manners - ship flowers from halfway around the world in an aeroplane for example - then that's to everyone's detriment as it wastes non-renewable resources.
Everyone benefits from transportation to some extent but that certainly doesn't mean that encouraging more of it increases the benefit.