The poker plate requires that you already have a poker case to put it in. The sandwich case includes the plate and all the pieces to build the whole case.
The sandwich case will be more expensive because you are getting multiple plates cut rather than only a single plate in the case of the poker plate.
Just draw both cases in my tool and you will see the difference visually.
Also, you can just use the switch plate and bottom plate with spacers to keep the cost down. Or cut the middle layers out of acrylic to keep the costs down.