I had to do a little research just for fun. It is almost exactly 200 more miles of driving to drive as opposed to taking the ferry. So if you figure how much gas you'll use on those 200 miles you can compare it to the cost of the ferry. At 15 MPG and $2.80 US gas price, it comes out to $37.33; 20 MPG - $28.00; 25 MPG - $22.40. Of course you have to consider other vehicle costs (maintenance & repairs) but for most vehicles this would be negligible in 200 miles.