Another option is “camping cabins” (campsite, structure with beds - bring your own sleeping bag; usually no bathroom).
Examples I know about:
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In Custer SD near Mt Rushmore and Crazy Horse - $55/night (not a bad deal when just a campsite these days can be pricey).
https://gfp.sd.gov/camping-cabins/ -
KOA chan has camping cabins, usually pricier I think. Sometimes communal kitchen area.
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Steamboat state park in CO has yurts.
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Horsetooth Reservoir near Fort Collins as camping cabins $90/night (and maybe discount off season?) - great view, but you have to carry your stuff downstairs from parking lot. Shared outhouse.
The trick is that often the reservations for this kind of thing fill up quickly. We never seem to be able to plan local things far ahead, since we concentrate on planning our distant travels.