Au contraire!
The greedy assholes have found out they can charge that much, that's why they do it!
Look into staying in Wyoming, Newcastle (good food and lodging)is just 60 miles away from Sturgis along one of the pretty highways.
8 miles up the road toward Sturgis is The flying V. (castle of the black Hills) lodging.
They have a huge area behind the place they let campers stay for free when I lived in the area.
8 miles up the road from that is Mallo Camp Motel ( 40 Miles from Sturgis) you will have to ride 4 miles down a well maintained highway (no big deal used to take my Harley two wheeler in and out of there because I lived there) turn in at four corners, Wyoming,rooms and community kitchens, community sitting areas. You may even swing a deal to take all 6 rooms on one side of the hotel with a family kitchen or take the ten rooms on the other side and use the commercial kitchen. Clean, peaceful, located in the pines, or try state campgrounds located further up the canyon on beaver creek right across the south Dakota border. You may even get a room at the four corners Inn on the Highway but I doubt that?
you will have to ride 4 miles down a well maintained highway (no big deal used to take my Harley two wheeler in and out of there because I lived there)
Sorry! Amend this to say well maintained gravel road.