I asked them on facebook and this is the reply i got:

"It states "FREE Drifting, Car Show, Car Meet and SPL Sound Off" The event fee to enter into the gates is $20.00/$15(w/flyer). Once inside there are no additional fee's with the exception of ride-a-longs. Msg me if you have any other questions regarding the event, We understand not many events have ever been ran like this if not any so there is bound to be some confusion."

Sooo im guessing everybody pays the $20 at the door.