While it has low capacity and was "replaced" with other ways to cross the Elbe, it still helps ease traffic across the river, other roads and bridges are often very packed or even blocked (often WW2 bomb defusals). I have lived both in NYC and in Hamburg and while the scale in Hamburg is way smaller, the type of traffic is kinda similar. Btw, isn't the Holland tunnel from NJ to Manhattan also free?
Also, we generally don't have tolls anywhere in Germany. If we do I have a hard time thinking of examples. Our taxes are (too) heavily invested in road infrastructure anyways and the tunnel isn't privately owned.
Right now the "Alte Elbtunnel" is undergoing maintenance in one of the two tunnels. Since as long as I've lived here, it hasn't been open to cars, but the large elevators previously used for cars are still serving bicyclists and pedestrians during the daytime. They get quite full during rush hour.
