GGB Only on paper. An understaffed shift caps how many covers the room can serve, slows table turns, pushes the team into overtime and eventually churn — and the wage saving is usually smaller than the revenue and recruitment cost it triggers. The honest comparison is the loaded cost of the extra shift against the contribution of the covers that shift enables, not against zero.
From How Many Staff Does a Restaurant Need? The Staffing Math — the full reading, with the method behind this answer.