Granting your premise, i'd be forced to argue that economic value (as such) doesn't arise from their activity either -- which i think is a reasonable position.

Ie., The reason a cookie is 1 USD is never because some "merely legal entity" had a fictional (/merely legal) desire for cookies for some reason.

Instead, from this pov, it's that the workers each have their desire for something; the customers; the owners; and so on. That it all bottoms out in people doing things for other people -- that legal fictions are just dispensble ways of talking about arragnemnts of people.

Incidentally, I think this is an open question. Maybe groups of people have unique desires, unique kinds of lives, a unique time limitation etc. that means a group of people really can give rise to different kinds of economic transactions and different economic values.

Consider a state: it issues debt. But why does that have value? Because we expect the population of a state to be stable or grow, and so this debt, in the future has people who can honour it. Their time is being promised today. Could a state issue debt if this wasnt true? I dont think so. I think in the end, some people have to be around to exchange their time for this debt; if none are, or none want to, the debt has no value