Acceptable loss rates vs. pyrrhic victories?

[Felix C]

Have been reading regarding anti-shipping strikes in the Med. and ask if there was an acceptable loss rate/exchange rate for sinking a merchant ship or warship type.

Example being the strike which resulted in the loss of the transport Rohna expended eight He-177s. I guess at the time the Germans would have only believe they sunk a merchant ship, not also 1000 lives. So would one merchant ship be acceptable loss rate for eight aircraft?

I read where the Allies acknowledged an acceptable loss rate in heavy bomber strikes and so ask if the Ger/Ital powers had similar. I realize the Allied heavies were used strategically and a convoy strike is tactical. But I note the campaign on Malta and Med convoy strikes could be quantified in terms of how many sorties could be launched before the squadron was ineffective.

I guess that also leads to the next question if there was an operational resarch section established for extended fronts. I am thinking in terms of Malta which was repeatedly bombed and is a relatively small target. Was there a calculus done of how many bombers/sorties would be required to neutralize a specific target or targets?