Trade very much is zero sum, at least some of the time. Prices are set by power disparities, not by abstract concepts of relative value.

One of the many problems with mainstream econ is that gloms together a whole set of unrelated interactions in a single crude concept of "price."

In reality share dealing, corporate wage bargaining, negotiations between farmers and supermarket chains, lemonade stands, and tourists haggling with craft vendors on vacation are all completely different kinds of interactions.

They end up with a price because they're mediated in currency, but their differences are far more interesting and economically revealing than their very superficial similarities.

This is perhaps the broader point, which is that to the degree economics acknowledges non-priced value it’s a hand wave to “there’s some economic surplus here otherwise these people wouldn’t reach agreement to exchange”.

But to the degree that senses of value are the motivating factor behind economic exchange it’s oddly absent from the discussion. I get the reasons: philosophical inquiries about value and aesthetics are a lot more challenging to work through than concepts of utility reflected by measurable actions, but this goes to the overall point about the limitation and overreduction of current mainstream economics, and the criticism of people like Graeber of its politicised and somewhat arbitrary intellectual grounds.

To the degree mainstream economic reduction is useful to support understanding that’s fine - it absolutely allows reasoning and insight in many scenarios, especially microeconomics - but to the degree that decision-makers double down on it (especially macro) despite it being incomplete or absolutely wrong in certain environments and contexts because it promotes certain power structures and power plays that is highly problematic, especially when people jump to its defence out of misplaced loyalty to a school of expertise.