I was searching the web for a jumbo guitar, and kept coming up with different nut widths on the various options. Finally, I typed "jumbo with a 1 3/4 inch nut width" into the space provided on "Musician's Friends," and most of the options that came up were top-of-the-line Martins--which aren't really full-sized jumbos--Gibsons and Taylors.
             Epiphone, Washburn, and most of the others had narrower nut widths that went down to 1 5/8 inch.

             I wondered if that had something to do with the cost of materials to manufacture a wider neck, without using laminate, or a softer wood.