Was the Bombing Campaign against Nazi Germany Worth the Cost?

From Jonathan Yardley's review of The Bombers and the Bombed by Richard Overy:

Was aerial bombing — “strategic bombing” — worth the cost, not merely in civilian lives but in those of pilots and support crews, where the attrition rate was unusually high, and in the cost of researching and manufacturing a vast, modern aerial force? Obviously there can be no conclusive answer, and to this day powerful forces inside governments around the world argue for the ostensibly sanitary strategy of bombing — these days, by drones — as opposed to ground warfare employing human troops, but we have good reason to believe that at least in World War II, the bombing campaign cost more than it earned.

To understand the question it helps to know that the Allies devoted gigantic resources to the bombing effort; the British were devoting 40% of their military budget to the building and flying heavy bombers. Yes, the bombing damaged German industry, but it did even more damage to British industry by taking up so large a share of productive capacity.