Campsite prices vary based on utility availability (i.e. primitive site, electric/water hookups). I believe they are about $30/night during the Summer, give or take. They do have a store and bathrooms w/ showers.
Yes they have a general store and showers in the restrooms. The cost depends on the site and if it has electric. Check out reserve americe.com. If you do a search for Hamlin for tent sites it should pull up a map of the campground.
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