I don't think there's anything in terms of conventional accommodation or fast food in Camp Mather, unless you go back to Groveland, or press on to the Yosemite Valley. It's really remote..
Camp Mathers has no reasonable prices hotels. It's out in the middle of nowhere and you will pay to stay there. It is a nice area with a small store and restaurant etc. Fun place to walk around in. No fast food is there either.
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