$100 per night

Try finding an oceanfront campground in the Myrtle Beach area, or anywhere around Disneyworld for a nice campground, for less than $100/night (full hook ups) during the summer! The more "resort like" campgrounds get, with all the bells and whistles so many are now looking for, the more they're going to cost! Would like to know how much a decent motel room, at a place with a pool, scheduled activities, store, etc. would cost in the same area? Bet it's a good bit more than the cost of a campsite, and you still have to go out to eat every meal! We often seek out state parks where we can, but still find the cost of a campsite almost always much less expensive than anyplace else to stay - and you're in your own bed every night!
As was said, supply and demand - open market! If people pay it, owners will ask for it to be paid. DH is a retired tax assessor - he told me campgrounds often pay through the nose in property taxes - land values are determined as commercial property, and some states determine taxable value based on the number of campsites available and income each produces. OUCH!