The cost of a site is going to be based on the amenities the County Park, State Park, Army Corp of Engineers Park. RV Resort, etc, include. If you want a 5 star resort, you're going to pay the price and most likely have a newer RV. If you like primitive camping in a National Forest, you can get by really cheap.
Unless your expectations are unreasonable, you can get nice sites for a reasonable fee.
Fathers Day weekend, we went to a Motorcycle Rendevous at Blaney Park in the Michigans Upper. Camping was free, it was primitive, but you could spend the whole week if you wanted to.
Most every Michigan State Park Campground offers electric only sites for around $26 a night, if you want a premium site you're going to pay extra and for weekends you need to book two nights.
Most of Michigan's county park campgrounds are about the same price.
This coming weekend we are going to Stafford Park, Huron County, Electric only Lakeview site $26 a night, two night minimum on weekends
Next weekend it is Otsego Lake County park, 30 amp electric site that will handle a 40 footer is $26 a night, two night minimum on weekends
Labor Day weekend we are heading to Chain O Lakes State Park in Indiana, a nice electric site that will handle a 40 footer $111 for the weekend including all fees.
We are heading to Tennessee for on October 12 staying at a private campground on the way down, visiting several state parks during our stay, and culminating with 4 nights about 7 miles out of Nashville. We will be heading home on on October 24. Total cost for 12 nights of electric campsites under $300 with most being pull through sites.
The deal of the trip is Nashville, senior rate for a standard electric site $11 a night. You will need to do your own homework if you want to find that deal.