Interior work is both spacial and atmospherical. with many tools like texture and coulour, light, even soundscape & odours. It encomprises functional use, mood setting, theming goals, exhibit schemes. The interior design accounts for an allsided real environment and real use.
Show set design & building, however, is a different section from general interior design work, as it only has a viewable 'front'. At a set, we face the goal of 'make-believe' without the functional use the shown set would offer in the real world. As criteria are different, so also is the specific budget.