Is $900 to locate a buried well head a fair price?

I inherited a house in Northern Maine, built in 1951, that has a well, but I'm having trouble locating the well head. The house has a 1/2 hp pump in the basement with two pipes going directly into the dirt floor, which I've traced to the basement wall where they exit. I'm unsure if the absence of a submersed pump means the well head is not on top of the well itself, and there are no electrical wires running with the pipes. I'm also wondering if the well head could be completely buried several feet down, or if something should be sticking up. I'm trying to determine if I'm limited to hiring someone with ground penetrating radar or drilling equipment, or if I can find it myself. I'm also curious if the pipes exiting the basement wall indicate anything about the well's location. The house uses city sewer, and residents decades ago rejected city water. I've checked city/county records and online databases, but our street is a blank spot for wells. Everyone who knew about the well has passed away. I'm planning to add a room with a bathroom onto the house and am concerned about building over the existing well pipes. There are no outbuildings or outdoor faucets connected to the well. I've been looking for the well head without luck, and there's a dirt/trash pile 75 feet from the house that might be hiding it.