"These ARE contradictory, because if every society has replicators, then in theory each society would have all the things it could possibly want, and there would be no scarcities of items to create demand. Certainly there'd be no reason to transport goods from one planet to another, since replicators in each place could just produce whatever you wanted. "
I think I can clear this up as written, but I'm not saying that makes them credible possibilities in real life.
The reasons for what you pointed out are that only the Federation (and some other races, independently) have replicators. Most do not, so they still have more typical economies. All races have pretty strict rules about sharing technology. The Federation in particular does not do it because of the "prime directive"; they do not want to alter the normal evolution of other societies. Other, more hostile, races do not do it out of power.
It's probably also worth pointing out that replicators are more like ultra-cheap energy, rather than free. They do create an energy drain on the reactor of anywhere they are used. You can see this in the Voyager series, when they often need to shut them down due to being unable to refuel the ship.
Anyway, that's the explanation given that resolves the issues you point out.
Money, oddly enough, you mostly see with the Ferengi, despite them having replicators. I suppose they felt that was necessary to create a caricature race to use as a foil for the Federation. You occasionally see Starfleet officers using currency, but only with other races. Sort like how US paratroopers had foreign currency and gold in their drop packs.
I may watch too much Star Trek...
Ah, okay, that makes a lot more sense! Yes, you've definitely watched more Star Trek than I have, and probably more recently as well.
I recall that energy was a problem, but what about the manufacture of replicators themselves? Do we know if replicators could make more replicators?
They had these things called industrial sized replicators that were necessary for constructing super large objects (or even moderately sized ones, like other replicators, which were sort of appliance-sized). They had these at Earth, on shipyards, etc. They were powered off of reactors that may have been too large to fit on a ship, I'm not sure.
In some cases, ships had to replicate huge stores of items for emergencies, like medical supplies. This would lead to power drains that required them to refuel with "dilithium crystals" at a port. Under normal operation, a ship wouldn't need to refuel more often than...I dunno, maybe a year or two, but serious replicator load could cut that time substantially.
Given that replicators produced items almost instantaneously, the only advantage to making more replicators was to slightly speed that process up. They still need to be attached to something like a reactor. I never saw a portable replicator in any of the series, they are always attached to a ship or a reactor at an installation.
That's super interesting--so what we have, then, is an economy in which there are just a few potential bottlenecks: dilithium crystals for energy (for both production and transportation), the large size, limited number, and limited locations of industrial replicators, and then the fairly minor limitations of small replicators for meeting everyday human needs. And, as long as those limitations are overcome by securing a supply of dilithium crystals and managing industrial replicators, the rest of human needs are met: space communism, indeed.
Presumably there are also some things that replicators couldn't do. I recall Whoopi Goldberg having to mix cocktails with a particularly delicate touch, because (apparently) replicators couldn't produce something so volatile. So it did still make sense to have "service" jobs. I don't recall things like haircuts or childcare coming up much, but I suppose those would also be things that relied on humans, and thus would have to be organized in some way.
This has been a great conversation, by the way. Thanks.
Yeah, you can't really replicate a "Flaming Moe" too well. It's all about the process, not the result.
Dilithium crystals also seem to be so hyper-efficient that acquiring them only seems to be a problem if a ship is stranded far from a port for literally years.
By the way, there's another good comment thread going below.