Joez is right on your type of unit affecting the rate. Also the number of people full-time living in the rig, vs going to work or outside the rig all day.
Our rig (50 amp class A) also has 2 ac units. We're just 2 adults retired, going on 4 years full-time living, traveling, camping. Traditionally, we only use the front TV, the laptop and printer on a daily basis. We do not have laundry facilities or radiant floor heat. We ALSO have no solar power generating capabilities...just a generator for boon docking.
When parked monthly, (vs on the road traveling, or overnighting) we use electricity (vs propane) for the water heater and refrigerator. We also cook more when parked for a couple months, so the convection oven plays a strong role in electricity use. Of course the coffee pot goes on every morning.
If we're parked in hot weather for the season, those ac units can really suck down electricity.
We can run $80 to $150 a month in hot weather. Offset a bit by limited convection oven cooking. Too hot to cook inside, so the BBQ (non electric type) gets a workout when it's hot.
When we're parked in cooler weather for a season, we use a very efficient space heater in the mornings to take the chill off. Perhaps the electric blanket if we're having a cold winter in the desert SW. Generally run $40 to $60 a month in these climates.
I unplug stuff (and switch the water heater off) when not in use. (The coffee pot, electric blanket, space heaters, computer), probably only saving myself a couple bucks from parasidic electricity consumption, but it makes me feel better.
I also donated my holiday rope lights to the kids, converted to a MUCH lower consumption LEDs and solar lights. Was totally amazed how much power those old rope lights consumed (additional 50 bucks) over the holidays!Ree makes a VERY good observation.
DO read your meter when you decide to book for a monthly rate. Mistakes happen, and can be overcome if YOU have taken the time to read your own meter. We too had a horrendous electric bill the first month at a snowbird park. $380. I knew we couldn't have used that much if I had wrapped ourselves in rope-lights. Because I had electricity records from their sister park, we reached a consensus ($80). I'll never forget to read my meter again.