To address bugleyman's point of suspension of disbelief:
In his Revelation Space books, Alastair Reynolds writes of "lighthuggers", massive starships approaching high percentages of C, and crewed by less than a dozen individuals. Reynolds makes it work with a strong degree of automation and crews of cyborgs, plus he uses the speed of light as an absolute. IMHO, his world building works because he blends his fantastic and familiar in a particular way.
An example IMHO where the familiar begins to not work is in Star Trek. Enterprise-D is crewed by a thousand people, which would make sense for a big ship. But what do they all do all day? It's always the same twelve people actually doing stuff. Chief O'Brien hangs out in the transporter room waiting for someone to beam out? That guy in the brig just stands behind a panel and likes it?
The bottom line is this: if the story (or adventure path or campaign) is engaging and entertaining, the storyteller will find a way to make these details work to strengthen her story, or decide these details really don't matter and find a way to work without.