Use ～ばそれまでだ to state bluntly that once a certain condition is met, everything is over and there is no recovering — effort, plans, or assets all become meaningless. It typically frames a worst-case scenario in warnings, risk assessments, and negotiation leverage, so it's common in reports, proposals, and pointed remarks in meetings. Often paired with どんなに〜ても or いくら〜ても to stress that prior effort counts for nothing.