Since Grosse Ile is an island, you have to take a bridge to get over to. There are two bridges that connect the island. The other bridge is the Wayne County Bridge and it is free.
This one is the Grosse Ile Toll Bridge and is $5 to cross. But that $5 is both ways, so I guess it's not too bad.
The bridge was built in 2013 and based on the fact there is a Ferry Road, I assume it replaced a ferry that went from the mainland to the island. This one is a swing bridge and reminds me of a bridge that used to be in Bay City.