Yes the full cash rate plus the $3.95 a rental day so a week rental but only use it once to cross the Verrazano Bridge in NYC would be $35.75 ($19.75 plus $16 cash toll instead of $11 EzPass).

For EzPass you can get one even if you do not own a car. Picked up at a crossing but when registering online you can't do it. Website won't let you get around entering a car registration and you have to call them.

After they explain on the phone that even though its your EzPass violations (speed, non-payment) will be issued to the license plate of your rental and you could face additional fees from the rental company they registered the EzPass. When you get one at a toll it is only active for 48 hours you have to register it.

I got one, don't own and car and have not had any issues.
My experience.