Styling shots use three times what a real room needs. Here is the honest number for a given ceiling height.
A styling photograph is built for one camera position. The arch is dense because it has to fill a frame, and the frame is two metres wide. A real room is looked at from everywhere, and density that reads as lush in a photograph reads as crowded when you are standing under it.
For a standard two-and-a-half metre ceiling, an arch over a three-metre doorway wants around sixty balloons, not the hundred and eighty a styling shot would use. Go higher and the count rises with the visible area, not with the height: a four-metre ceiling needs perhaps ninety for the same doorway.
The other saving is in the clusters nobody sees. Anything below waist height behind a table is spent for no return.