> An economic transaction is an exchange between people with needs (, preferences, etc.) that can die

You’ll need to give a citation for this to take you seriously

A transaction is an exchange between two parties of something they judge to be of equivalent value (and mostly, in ratio to a common medium of exchange).

You can program AI with "market values" that arise from people; but absent that, how do these values arise naturally? Ie., why is it that I value anything at all, in order to exchange it?

Well if I live forever, can labour forever, and so on -- then the value to me of anything is if not always zero, almost always zero. I dont need anything from you: I can make everything myself. I dont need to exchange.

We engage in exchange because we are primarily time limited. We do not have the time, quite literally, to do for ourselves everything we need. We, today, cannot farm (etc.) on our own behalf.

Now there are a few caveats, and so on to add; and there's an argument to say that we are limited in other ways that can give rise to the need to exchange.

But why things have an exchange value at all -- why there are economic transactions -- that is mostly due to the need to exchange time with each other because we dont have enough of it.