Instead of putting 150 of the B17, B24, or Lancaster size bombers in the air, comparatively the Germans would put 200 of the medium He111's and "light" heavy Ju88's.
Remember, the Ju88 can carry more ordnance weight than the B17. It just doesnt have the defenses, range, or speed. The Ju88 didnt really need any of that considering where Germany was bombing.