I read a more detailed explanation of the star trek economy. I can't find the link now [1] but it answered some of the questions raised in this post. Since I can't find it I'm not sure if it was canon or just fan theorizing, but it was interesting all the same. I understand that this is a highly nerdy topic, but it's an example of how a a Proto Post Scarcity economy could work.

As I understood it, every year in the star trek universe citizens would request what they wanted and say what they were going to contribute to the economy in exchange for thaose things. ie, Captain Picard might say "I want to make improvements to my farm in france, a new personal transportation device for a relative, X number of paid for vacations and the daily luxuries of being a starfleet officer. In exchange for that, I'm willing to be a starship captain for the next year". Then an elected committee would review the request and approve it or deny it. I remember that it was noted that the committee had to be from a different area or state than the applicant. ie, a committee in Florida would review requests from Texas. Essentially it was a "That sounds fair" economy, based on judgement instead of currency.

As I recall, daily needs like food, shelter, medicine were taken care of for everyone, at various levels of luxury based on what the person was expected to contribute. Starfleet officers frequently talked about credits, either when gambling or visiting a bar on a non-federation or non-participating planet. I imagine this was a sort of legal black market system that would allow people to exchange money between one another to settle debts and to spend in other cultures, not really for routine living expenses. Post scarcity does mean post money, but there still has to be a way to maintain personal ledgers (maybe the credits were a year 2364 version of bitcoins?)

I think that Gene Roddenberry and other science fiction writers envision post scarcity societies for two reasons: 1) Money causes problems and 2) Economies function more efficiently without money.

We all love money, but think of the harm it can cause. Crime, ruined relationships, greed and the general oppression if not outright murder and enslavement of millions of people throughout history. As we all know, whenever someone says "It's not about the money", it's about the money. A moneyless world would solve a lot of these social problems. It's not that wealth is a bad thing. It's great to be rich. But a lot of problems arise when people need money for their daily sustenance. Food, housing, clothing, entertainment. All of these things should be taken care of at a low level, with compensation from contribution providing nicer and more desirable lifestyles. And it's quite possible that getting rid of daily dependence on individual spending is the best way to supercharge an economy. We don't see the waste in modern capitalism because we're primarily concerned with our own wealth, but it's there. Think about how much is wasted on a national (or galactic) scale. The efficiency gained through improved economic function would be more than enough to pay for all the replicator time that everyone on multiple worlds would need to live well.

Like many great things, the idea of post scarcity / post capitalism started in science fiction. But it doesn't have to stay there. We can start building a world where everyone has comfort and the rich have luxury. There are things we can do today to move us closer to this ideal and move people away from a system that's designed to make us all slaves to small amounts of wealth. I'm looking at you, Basic Income.

[1] Why hasn't someone made a startup to solve this problem? I'm constantly thinking of things I read and potentially bookmarked years ago, but google is a black hole. I would pay for this.