Not a dumb question, and it can vary for different companies, depending on their setup.  It also depends on the garment.  Regarding transportation, the extra cost depends on the method of shipment, how heavy the garment is in general and how much space it takes up (for example, a sweater/winter coat vs a tee shirt). At the retail level, there is definitely an added cost in having to include every size on the shelves. This is why many retailers only include a certain size range in brick and mortar stores, and the rest need to be ordered online. (the exception to this would be retailers that only offer plus size clothing, obviously)