[dotancohen]

I believe that the saving four hours (two hours each way) to travel from or to the city, multiplied by the amount of current and potential vehicles, is a clear opportunity benefit.

Not to mention the fuel saved and pollution prevented. And increased economic development for the city.

[Hnrobert42]

No. The opportunity cost is that if you build a bridge to nowhere you can't build a bridge to somewhere else more useful .