Yes there is a $25 fee for tent camping and $40 for no hook up grass RV parking. That is for the entire weekend Fri-Sun. Camping passes are available on the website in addition to your single or multi day passes to the park.
http://www.barbervintagefestival.org/Tips on tent camping at the festival if you have not been before.
If you can swing it get in early for the better spots. look for high grassy ground. Do not be lured by the nice view down low by the lake edge. If we get rain it becomes a mud bog.
If you care coming by car get a spot as close to the main loop road as you can. You will only need to hike to the road to catch the trolleys that run the entire loop around the facility and can drop you anywhere. Again if you are lured by the pretty view down by the lake you will have a long walk to and from the trolley all weekend.
If you come by bike plan on using it to get around most areas. There is plenty of bike parking at all the major stop points around the facility. It is nice to be able to just hop on and ride to see something else. Helmets, license plates, and registration are required to operate a motorcycle or scooter around the facility.
If you go out for dinner away from the campgrounds be watchful of weather and temps. Twice I had to come back into the campgrounds in near white out fog. There are lots of low lying areas and plenty of ponds/lakes in the area. The fog can just roll in and sit in those hollows and valleys. Riding a vintage bike with street tires through a mud bog in dense fog on a pitch black night is sure fun let me tell you.
Go by to sign the waiver and get your paddock pass wrist band at your first reasonably free time. There is no cost for this but the tent is only maned during day time hours for the waiver. Having your wrist band makes it easier to get in and out of the paddock after those hours and this is where the shower facilities that are open to tent campers are located.
There is a gas station just down the road from the facility entrance that is well stocked. If I am on a bike I will typically go find my camp site and setup first. Once the bike is unloaded I make a run back to the gas station for bottled water, ice, and beer. There is really no problem getting in and out of the facility at any time so is not like you have to get in and not leave the entire weekend.
The campground area is primitive. There are port-o-johns but no electricity, water, or brick and mortar bathrooms that are close to the camp ground. There is also no shade or shelter in the campground itself either. In the 5 years I have gone I have experienced temps from the 40's to the 90's. Pouring rain to cloudless sky with intense sun. If you are coming by car/truck plan on some shade if you can. I bring a Ez-Up when I car camp.
If you car camp bring your helmet, jacket, gloves, proof of motorcycle insurance, and motorcycle endorsed drivers license. Both Ducati and Triumph are usually on hand with the demo trucks. They lead 20 to 30 minute demo rides all weekend. They require the above items along with long pants and closed toe shoes to sign up for rides. Last year I took a Ducati 1100S Hypermotard out twice for a ride.
Bring your camera and plan on shooting a ton of pics.