They are open all year long, however they are usually booked up several months out so you have to book early. I don't believe they were over 100$. https://washington.goingtocamp.com/Mobile/ You can look up prices amd availablity there.
Not sure...they look like nice places though. I was there once this past June. It was nice. They have showers as well.
I was there Sunday the cabins are rustic and private and shower/restrooms are not far away..
About 35 to 60 open in winter need reservations
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