〜ばそれまでだ／〜たらそれまでだ

Meaning

Indicates that if it comes to that, everything is wasted and it's over. States the conclusion "that's the end of it, beyond recovery."

Examples

どんなに貯金しても、病気で倒れたらそれまでだ。 No matter how much you save, if you fall ill, that is the end of it.
記録が残っていても、読まれなければそれまでだ。 Even if records remain, if nobody reads them, that is all there is to it.