Hood's lifetime cost needs inflation and class-size context

Could HMS Hood really have cost about nine billion pounds over her lifetime?

Only under a modern-value conversion; her historical build and refit costs were far lower, and sister ships might have reduced some unit costs.

Hood's approximate six-million-pound construction cost is checked against the much larger lifetime figure raised in the question. Refits and inflation increase the historical total, but a value in the billions must depend on a particular conversion into modern money. Building more ships of the class could reduce some per-ship costs by spreading design, facilities, and repeated work. Substantially different sister ships would weaken those savings and might not lower Hood's own total very much.