Wow!! Many are finding inexpensive RV resorts in their areas! Try going to San Diego or Temecula or Paso Robles, CA especially during a popular time. Nice RV parks will easily run you $75-$100 a night. Motel 6's are often the same price in those areas. RV'ing at nice RV parks in popular areas is getting very expensive. Not long ago these same parks were $30.
In other not areas or off season I can find nice parks for around $40-$50 a night. Anything less is a dirt lot dump with hookups.
One of the most basic dirt lot RV parks I've stayed at is the Lost Hills, CA KOA. It's $41 a night.