The reason circulating money adds to the economy is the assumption that circulating money equals work, and work improves life on the planet.
That's the most stupid bullshit I've read in a long time. [...] Or, in other words: Those $100 of money have turned into $700 of wealth.
That's what I said.
You are clearly confusing cultural value with economic value.
I'm not confusing it, I'm distinguishing it. Economic value is an approximation of cultural or moral value or whatever you want to call it. Quality of life basically. We can do things to economic measures to bring it more in line with something meaningful by applying things like inflation and PPP adjustments. It's still just an approximation which we bear out of necessity.
When it comes down to a single individual and a small list of actions, though, it is possible to make more precise judgments than just counting the number of dollars that circulate. If you give a random person a billion dollars, they might just sit on it and live a comfortable life and make their kids rich and just kind of trickle the money out for a few generations. Or they might be another Elon Musk and make strides in the space industry and electric cars. That's a big difference.
The problem with your original post was taking some crap you learned at university ("rich people hoard money in conservative investments, poor people spend every penny, so giving money to poor people results in greater overall economic stimulus") that spoke in generalities and large groups, and applying to a specific person like Bill Gates.
You spoke of scientific evidence... well where is your scientific evidence that Bill Gates himself spends like an average rich person? He doesn't. Most rich people are not tech-savvy philanthropists giving away billions with the specific goal of improving life through the application of technology.