I've been to two different ones in California. These two were set up by the quilting guild of which I was a member. There would be an announcement of the event through the guild. Usually cost about 200.00 per weekend from Friday noon to Sunday - all food included. We slept in a dorm like affair - there were about 125 women at each of the retreats .. and the shower arrangements were just a slice above college gyms. But we had a great time.
We all took our equipment which included our machines, irons, cutting boards and whatever we needed to go with all that. We usually had a "mystery quilt" going, lots of drawings, plus what we were working on individually. There were tutorials given and lots of questions answered. This was all done in a very large room where each of us were at an individual table with enough electricity outlets for whatever we needed. We sewed as late as we wanted - all night if anyone wanted to. And many were up at the crack of dawn sewing in pj's. It was fun.
I didn't know any of the women there, except by sight. There were lots of women there who did know several others and were good friends. But no one was slighted by any other. We all had a good time and I wouldn't hesitate to go on another if I had a chance and the bed was comfy.