Setting aside for the moment the other questions surrounding this topic, and addressing just your main point in this comment:
The fact of the matter is that we do not have the data to meaningfully estimate numbers like this, not even to an order of magnitude, not even to ten orders of magnitude, and it is best to admit this.
Fortunately, we don’t need an order of magnitude to make meaningful decisions. What we really need to know, or at least try to guess with better than random accuracy, is:
The sign (as opposed to magnitude) of the marginal effect of spending a dollar on X.
The relative magnitudes of the marginal effects of spending a dollar on X vs Y.
Both of these are easier to at least coherently reason about, than absolute magnitudes.
Setting aside for the moment the other questions surrounding this topic, and addressing just your main point in this comment:
The fact of the matter is that we do not have the data to meaningfully estimate numbers like this, not even to an order of magnitude, not even to ten orders of magnitude, and it is best to admit this.
Fortunately, we don’t need an order of magnitude to make meaningful decisions. What we really need to know, or at least try to guess with better than random accuracy, is:
The sign (as opposed to magnitude) of the marginal effect of spending a dollar on X.
The relative magnitudes of the marginal effects of spending a dollar on X vs Y.
Both of these are easier to at least coherently reason about, than absolute magnitudes.