all we know is that they don’t use money, except when they do. The writing is sort of fuzzy on the matter, which results (regardless of the intention) in an economy that doesn’t actually seem that different to our modern day in practice
At most they use credits, which at least according to this guy, are at most a peripheral, 3rd party currency, or at least a currency the federation uses for external trade, and that’s what makes most sense to me. Why would the average person care about federation credits when they’re only used on border systems at most, and your home replicator can make you pretty much anything you’d ever want? To a person living in such a world, for all practical purposes there is no such thing as money in the federation.
There’s no money, but people still own businesses and talk about buying stuff, which allows for the economic system to fade into a sort of forgettable background space.
They never seem to talk about buying stuff unless it is out on the frontier, exchanging with foreign entities, etc. It also doesn’t seem like businesses in star trek (at least the above board, earthlike ones) aren’t anywhere near today’s businesses. To me, it seems that they are treated as family businesses, with limited “employee” count, and with each “customer” getting their service/food/item for free, within reasonable limits. It’s like going over to your family’s house for dinner. You don’t pay, you’re family and they will happily feed you (within reason). And it seems that businesses treat everyone like that.
There is no stock market, profit motive, costs of running a business. It’s all done out of the goodness of people’s hearts.