If the official specs are to be believed the JJprise is 725 M long (which is longer than a Galaxy class ship by the way.) and the Vengeance is about 2-3 times as long that means its longer than the prime timelines Enterprise (1701-F) from 2409 1 and 1/2 centuries later. How can Starfleet in the 23 century possibly have the resources to support a fleet of ships this size?