If you live in a large RV/mobile home, you will need serious accommodations including hookups. As you have found that can be expensive.
I full time traveled for 2 years. My average nightly campground cost was $7. I only stopped in RV parks a handful of times. Mostly I stayed at senior rates in our National Parks, forests or BLM lands. When traveling I usually stopped at the nearest Walmart Supercenter. Sometimes I just "stealth" camped. For example when in the Canadian Rockies, the campgrounds were often close to $30 for non residents. We spent a week or so camping near a church in the town of Jasper. We were out all day traveling and seeing the sights and only returned late in the evening.
If you choose to get a big rig and need hook ups that will greatly limit your camping choices and often the remaining choices will be expensive. Think about going smaller, getting solar panels and avoiding hookups and you can camp and travel for minimal costs.