Your best bet to economize on camping fees will be to use free or low-fee locations whenever possible. Some businesses like Walmart will let you stay in their lot for a night. Some of the people you'll meet at the events may know a place where you can park overnight. Freecampsites.net lists some boondock locations for when you don't need to be in town. National forest and state forest CGs are among the most affordable CGs, usually with no hookups.
The RV you choose may affect how much you can save. A class B or a converted cargo van can be parked almost anywhere without drawing attention, whereas a travel trailer or a big class A aren't very stealthy.
If you simply must have electric hookup, you will definitely spend a lot more. There are ways around the electric problem, though... solar panels and/or a quiet generator could see you through most situations. Personally, I've gotten by just fine with a solar panel unless I needed air conditioning; A/C needs a genny.
Mike G.
Liberty is meaningless where the right to utter one's thoughts and opinions has ceased to exist. That, of all rights, is the dread of tyrants. --Frederick Douglass
photo: Yosemite Valley view from Taft Point