Of the many garage sale customers one gets, there are a few who stand out because of some unique behaviour and characteristics. Most people arrive, take a look , make comments, ask questions and either buy something or leave. A few comments may be made and that's all.
At my daughter's sale he bought a university text from an art course she took. It turned out that he was very knowledgeable about art. There definitely was another side to him that showed he was no buffoon. He could discuss art with a great deal of authority.
He cruises around your sale with his constant chatter. Then he quickly choses several items, makes his purchase and leaves. He probably attends most garage sales and follows the same pattern of behaviour. I'm sure many of the people in my town will know who I'm talking about. Probably none of us know his name.