To unpack this claim:

> The value of something is "what you can get someone to pay for it." That is the only concrete, objective, and rational way to determine value.

Most if not all traded financial assets have conditional values, values that are fixed only at discrete points in time by actual transactions, and only in retrospect. Outside of that there's no guarantee that a stated value is concrete, objective, or rational at all.

The value of a given share of Bill Gates's MS stock for example is X if he attempts to sell a token amount today, and it's Y if he attempts to sell a large amount today. And X < Y all else being equal, a LOT less.

So tell me then, what is the concrete, rational, and objective value of Bill Gate's MS stock? The "correct" answer has to include a version of "well, it depends".

You claim that the value of something is "what you can get someone to pay for it" without realizing that by definition your measure of value is vague, indistinct, and subjective.

You could make an argument that the value of something is "what you actually got someone to pay for it at a specific date and time" but you didn't say that.

> I disagree- The value of something is "what you can get someone to pay for it." That is the only concrete, objective, and rational way to determine value.

That's perfectly fine, after all value, whatever definition we use, is just a model, nothing that exists outside of humankind. The problem with the definition you prefer, though, is the substantial subset of the economy that will not be available on a market. An economy consists of significantly more production and consumption than what gets sold on a market and therefore gets a price. Examples: Producing free software in your free time, creating music, training kids in a sports club, raising your own kids, teaching for free via youtube channels or moogs or locally etc. All these thing create, well, value, I'd say. They boost both wealth and efficiency of the economy.

That's not the only way, though it is not bad (as proven by the prosperity big parts of the world now enjoy). Mostly, it's easy and self-balancing. But as a way for solving the problem of resource allocation, it has some really bad failure modes - like creating tons of useless, wasteful work (zero-sum games like advertising) and steering us towards making our planet uninhabitable for humans.

A ponzi scheme has a net value of 0 or less at any point in time.

Just because some people can get out more than they put in doesn't mean a ponzi scheme has created any value for the economy as a whole.