One was a businessman who was excited to see how much the stock portfolio he had put together as a long term trust had fared. Picard had to gently explain to him wealth and money were no longer a thing.
Of course the Picard series itself then thoroughly destroys that thought by going on and on about money.
IIRC, in Star Trek, the replicator does not convert energy into needed material: it simply reorganizes existing molecules into a new form.
So, for instance, you can't use it to make yourself a bunch of gold: you could use it to convert a bunch of gold jewelry into gold bars, or vice-versa, but you would need some actual gold. It won't convert lead into gold. I think I heard or read somewhere in the lore (maybe non-canon) that the food replicators needed supplies of biochemical ingredients to use for making food. They could get that from various places, including breaking down the waste of the crewmembers, but they couldn't just conjure food out of nothing using pure energy.
And that unlimited energy has led them to a post scarcity, post money utopia, though that scenario seems to have been withdrawn a little in Picard.
Edit: Why would someone, say the Romulans, do that? Well, Starfleet doesn't establish contact, or invite a planet, because of some on going war or a non-unified government or no FTL tech. The Romulans step in, side with one party. They provide technology and weapons, they unite the planet as an "ally" or theirs. And now they have a new planet and systek to exploit, to use a base. Legally, and even better the Federation canot intervene. Rinse and repeat everytime Starfleet side steps a planet in a strategically important position. Do so over a couple of decades. You see were I am going, right?
They really seemed to make every race encountered to be a relatively peaceful semi-utopian culture.
Edit: For some reason, every non-FTL civization Star Trek just seems to be ignored by everyone. Heck, even the Dominion ignored them in their empire building...
That's authors so: In the Star Wars Legends EU there are the Ssi'ruuk. A species from the edge of the universe harvesting other lifeforms, litterally, for power generation. Throughout the books about them, the fact they could go on a spree of exterminating each and every primitive species they encounter is never mentioned or even hinted at. Nor is the fact, that with a bare 6 systems under their control, and inferior ships and tech, they should be one punitive expedition away from extinction themselves.
More seriously, the basic answer for the Federation in particular would be "amounts of energy". Voyager uses exactly that, with minor but consistent references to 'replicator rations' because they're limiting the total energy usage of the ship.
Are they all some starfleet officers toiling for decades on off-chance that one day they might get job on a vessel? The ages of people on show don't present that...
The whole post-scarity kinda really breaks down when you start to look at edges. As society would not be effectively be able to keep up the production at least not as shown in shows...
Now, if you want an Enterprise like personal spaceship, you probably are much better of being part of the Q continuum than the human race, scarcity wise.
Cumals.
You can give everyone as much food as they want (and we already do!), but you can't eliminate scarcity.
A cumal is the unit in which medieval Irish monetary values are denominated. It is also the medieval Irish term for a female slave; the unit is notionally equal to the value of one such.
The point of answering the question in a historical currency is to emphasize that this question is easy to answer by simply thinking "what have been some well-known historical currencies?"
People trade in materials, tools, food, livestock, and women.