My information says $15 a day per highway vehicle; you can tow 25 motorcycles or cars on a trailer and it's still $15. But if you have pit crew in chase cars, each car is $15 also. So, if you have a pickup, with a trailer, and inside the trailer is 3 bikes and one car, you pay $15. If your buddy follows you in his SUV, it's another $15 to him.
You can get a pass from SCTA for $70 for a year, which gets you 3 highway vehicles, but only on event weekends.
For a limited time, the unrestricted annual pass is going to be $80 (through Oct1?) per hwy vehicle.
There is a kiosk at the entrance to get passes, but for the SCTA discount, you must get from SCTA registration booth.
At least that what I remember from the Roadrunner meeting this week.