Complex sentence: Not all films that fail to earn back their estimated costs during their theatrical runs are bombs, and the label is generally applied to films that miss earnings projections by a wide margin, particularly when they are very expensive to produce.
Split into simpler sentences: Not all films that fail to earn back their estimated costs during their theatrical runs are considered "bombs". The label is generally applied to films that miss earnings projections by a wide margin, particularly when they are very expensive to produce.