Joshua Boos has multiple Amazon seller accounts to sell books: Sandy Dunes Surplus, FrogCreekMedia, NBSCA, Knowledge Pond, and at least a dozen others. But he does not have any books.
When you order a book, he will turn around and order one from some other seller and tell them to ship it to you. But he does not order the same grade of book. If you paid him $30 for a new copy, he will pay some other seller $10 for a used copy, and he pockets the difference.