This is quick entry for anyone (not from Bay Area) that might get a Fastrak ticket.
First, when you cross the bridge, you'll see many toll booths. Do not drive past the Fastrak lanes (even if it's 2am). Instead, go to a booth where there's a person there, and pay 4 or 6 dollars for a pass.
But if you did drive through, it won't be 100 dollars. My friend who lived around the Bay Area told me the ticket was going to be severe. To my pleasant surprise, it was only $30 which is a huge relief! It says that you don't have to pay the $30 if you sign up for Fastrak online. Don't do it unless you're planning on driving to SF daily/weekly. Yes, you don't have to pay $30, but signing up is not free. It costs $25 to sign up the the account, and some other complicated monthly fees.
When you go to pay your violation it'll say IMPORTANT NOTE: If you are a first-time toll violator, and you are not currently a FasTrak customer, you can have your violation penalty dismissed by opening a new FasTrak account sounds good huh!? Nope. Opening a new account costs $25.
My suggestion is to man up and pay the $30 dollars. And don't do it again!