"... And what happens when the stock gets to $60?"
And what happens when the stock stays at $5 (or lower) for 20 years?

"... And what happens when the stock gets to $60?"

Why did this "poor guy I sold it to" buy it?
I am not sure what you mean "What gives value to price differences at car market" If English is not your first language, you are doing very well however ! I think what you mean to ask is what causes the price difference in the used car market?
Also investors can be balancers , adding money&motivation where its needed.I started a company from nothing with a small venture capital round. The company now earns more in a year than the entire venture round. Those investors made good money selling their shares because actual value had been created. Hard to call that a zero sum game.
Even in those cases it isn't zero sum. Unemployement was sub-5% when I started my company, the employees I hired certainly had plenty of other opportunities and chose to work for us, so clearly they were getting something out of it. Absent significant employee exploitation, employees don't suffer negatively to an equal extent that the company does well, as would be required if that were indeed "zero sum".Gain might be others loss at least with human labour.
With robotics and automation it may be harder to classify loss if little maintance.
Rigging the playing field is also popular.
https://en.m.wikipedia.org/wiki/Lemon_socialism
Privatizing Profits And Socializing Losses seems like 1000+year old zero sum scheme.
%%Zero sum game, meaning someone has to lose for another to win, only applies to derivatives such as options & futures. With stocks this does not apply, everyone could be profitable.