Rick Webb, then Matt Yglesias, each try to figure out how the vaguely social-democratic post-scarcity economy of Star Trek's Federation works. Here's Matt:
Webb sees a welfare state, but I actually see something different. It's simply that energy is abundant enough that people have unrestricted access to consumer-grade replicators. Under the circumstances nobody needs to work to survive and there's really no point in maintaining a cash economy. But by definition improved technology can't increase the efficiency of historical production techniques. If the promise of Sisko's is a home-cooked New Orleans meal, then Sisko's can't partake in the post-scarcity economy. Similarly, you can replicate wine in unlimited quantities but a Chateau Picard vintage is by definition a scarce commodity. People appear to operate these businesses for roughly the same reason that Starfleet officers cruise around the galaxy—for a sense of personal fulfillment rather than enrichment.
The tl;dr: it's really about what near-infinite but still-expensive sources of energy would mean for us: much becomes worthless at home, but you don't want to be the guy paying the replicator bills out on the final frontier. And then there's the human hankering for tradition and authenticity, and the deep satisfaction of entrepreneurship, and aliens to do business with…
But we are forgetting one thing. Take the wine, for example. What could make Chateau Picard more than mere personal fulfillment, in a world where it's chemically identical to cheap replicator plonk? Pervasive DRM. If you really want an explanation for how and why a post-scarcity far-future economy would look, work, and think like late-20th century America and Europe, there you go.
