Complex sentence: The improvements made during 1990 overhaul could not save either of the California-cruisers, as by 1998, they cost about $38.8 million to man, operate, and maintain.
Split into simpler sentences: The improvements made during 1990 overhaul could not save either of the California-cruisers. By 1998, they cost about $38.8 million to man, operate, and maintain.