None of these people are solving any of the core needs of any of these other people (food, clothes, transportation, housing, any physical goods at all) and very little new money is entering this system at all, maybe some on the drop shipping side but that can also be a net loss in some cases. So yes this represents an economy but the denizens of that economy would be impoverished and miserable, constantly waiting for some outsider to come solve their problems. This is seen in the fact that most people do this as long as their pre existing savings can sustain it because they are doing it at a loss and then they give up when they have eaten through their existing wealth.

So yeah, i don't think it's much of a profound insight to point out the similarities to other economies just because of the existence of people engaging in trade with each other. The quality of the trade is the issue, not its existence.