You would do well to check if your beliefs are falsifiable. If you believe that GDP objectively, universally, and precisely maps to real-world value, no thought experiment will disabuse you of that notion.
Are you claiming that "GDP objectively, universally, and precisely maps to real-world value" is non-falsifiable? Unless you reason is that nobody can even tell you what real-world value is, that proposition can easily be falsified.
If you ever observe a trade that changes GDP in a way that does not correspond to the change in real-world value, the belief is shown to be false. Of course that isn't just a thought experiment, you have to actually do the observations.
I said something slightly different; I claimed the commentor's beliefs were potentially unfalsifiable, and then I characterized those beliefs as "GDP mapping objectively etc to real world value"
You would have to compare the GDP to some measure that better maps to real world value. And the choice of measure to use would be controversial. HDI? GNH? HPI? GNW?
I agree that GNP is a terrible measure of real world value (a lot of things increase GNP that decrease human well-being on a global or long-term scale). But if you want to falsify it, you need some other measure. Is the other measure falsifiable?
