The market proves this every day through the contracts they pay. But logic dictates that you cannot win a baseball game (the purpose) if you don't score a run. You cannot prove you've saved a run unless the runner was called out on the play. Therefore, in any case other than that you have to infer a run may have been saved, which is a hypothetical construct and not a real thing. It is only theoretically that one can show a run scored is equal to a run saved, but the math would have to work, and it doesn't because it cannot, because you cannot prove something didn't happen (wich is the basis of our legal system).