Over the past 12 years I've not noticed a significant difference in cost between KOA and other RV parks with the same level of service and amenities. The franchise fee does not seem to add that much, and sets a floor for the services to be provided.
I have stayed at RV parks with lower levels of service, at lower prices, and have been happy with those for overnights. I've spent many days on parking sites in public campgrounds that have offered little or nothing more than a place to park and a power hookup. You don't have to pay RV resort prices if that is all you want.
I am almost always on a gravel pad or hardpacked turf. A concrete pad means nothing to me, it forces me to use blocks to level, when I might not have to if I can move around on a gravel pad.