Actually, you have that a bit wrong. Walk in cost was "$3 per person or 2 for $5" per the FB page.
$15/car for show admission for two days? That's a freaking bargain.
$25/night for tent camping does seem a bit stiff. Was that per tent or did they mark off each site? Might be something to consider. Like an actual campground that allows X number of tents and/or people per site. That would make it reasonable.
DNW is a nonprofit, so nobody is in this for the money, but at the same time, they have to cover their costs. Putting on this event is not cheap.