Even under "homo economicus" rules, that's not true, because the marginal utility gain for that one person will be much less than the 999,999 people. Without diminishing utility gains, you have nothing like economics. I don't mean that rhetorically; none of the math works if the billionth dollar is exactly as valuable to a person as the first one, or the billionth orange is exactly as valuable to a person as the first one. There is no economics if what you say is true.

There's a kernel of truth there, but you have to open the gap much wider, many orders of magnitude wider, to the point it becomes more a philosophy question than one of economics, because the amount of money you'd actually have to give to one person to equal 999,999 very poor people getting $1,000 exceeds the amount of wealth in the world comfortably. (I don't even have to run the math; the exponential decay of utility makes this a done deal.)

I agree that it is a common error to mistake economics as being "about" money, one I think even at times PhDs in economics make, but it isn't about money. Money is merely one slightly special and easy-to-measure token in an economy, but it isn't really what economics is about.