> If I buy something from someone for $1 then sell it to you for $2, I gained a dollar and you own a share that's worth $2.
It's easy to see that this is nonsense: I could buy a widget from someone for $1, then turn around and sell it to my brother for $10000, does that really mean the widget is now magically worth $10000, and we doubled our collective holdings? No, what actually happened is that we together still have that same $10000, plus a worthless $1 widget.
Once again, the trade is within the context of a market and the market values the "widget", Apple Stock, Oz of gold or whatever as whatever people are willing to pay for it. That's how markets work. Individual Opinions are largely irrelevant.
It's easy to see that this is nonsense: I could buy a widget from someone for $1, then turn around and sell it to my brother for $10000, does that really mean the widget is now magically worth $10000, and we doubled our collective holdings? No, what actually happened is that we together still have that same $10000, plus a worthless $1 widget.