You shouldn't have to pay anything at all. There are signs for the Guest Dropoff, and the toll plaza folks will be happy to direct you as well.
While on this topic... this is something I really don't understand. When y'all rent a Towncar to pick you up at the airport, and take you to any of the Magic Kingdom resorts, they charge you extra, claiming that Disney charges them $9.00... That $9.00 is to park... There shouldn't be a charge for dropping off at a resort. Especially, since if you go via Vista Blvd, there is no toll plaza. And if you go after the MK is closed, Security does not collect money. *shrug*