Several campgrounds in the Wells, Ogunquit, Kennebunkport area that are on the local trolley route. Easy to get to good dining.
There is also a bus system in the Acadia area, that runs past many of the campgrounds.
There are several campgrounds in both areas that will run you closer to $50/night.
Use rvparkreviews to check things out.
Maine - Reviews of RV Parks and Campgrounds - RV Park Reviews