alt Hacker NewsI don't see how I've "lost the plot."
The comment you originally responded to does not presume market efficiency. In fact it carries the opposite assumption - if markets were efficient then the loss of economic value from weather forecasting would be immediately apparent and we wouldn't need to discuss larger-concept models with the goal of overcoming inefficiencies.
That original comment posits an idea of "economic value" that is independent from what can be captured by whomever is contributing to it, which is what you seemed to be rejecting.
The market efficiency it presumes is that an appeal to value is actually a rational actionable appeal to the government actor. That seems to be the whole point of the question (paraphrased) "can't you see the value of the thing we're losing" and speaking that to someone who stands to capture the value via tax receipts.
Of course if the government doesn't care at all about the 'market efficiency' of that value it's not clear why this question is even posed -- a hypothetically irrational rejection of the efficient projection of this value seems to be what the question contends with. The very question relies on a premise of someone somewhere acting with market efficiency on this data. With zero market 'efficiency' from the data, there's no useful market value generated whether you frame it as "capturable" or not.