Trading cards (and cryptocurrencies) are not like that. You can only make money if someone else is willing to pay more for it.
Correct me if I'm wrong, as I don't know much about stocks, but doesn't that require the company to have/pay out dividends? Otherwise you do require others to buy the stock when you sell it.
> Trading cards (and cryptocurrencies) are not like that
Don't know enough about trading cards to say that you're incorrect, but you're definitely wrong about cryptocurrencies. You can do various things to earn more without loosing your current amount, from staking (Polkadot), loaning (Compound) to getting rewarded for providing liquidity (Uniswap) or for doing nothing at all (Algorand).
If you make money along the way, as opposed to when you sell, then yes. The prevailing corporate playbook seems to prefer stock buybacks over dividends, which accomplishes roughly the same thing but only triggers tax liabilities for the stockholders who “cash out” by selling.
Obviously there is a limit to this process, but in a frictionless world of perfect financial knowledge a stockholder would always prefer the buyback approach since it defers taxes on the gains as long as possible.
And yes, a company would have to pay dividends, which is what I was hiding in my "in principle" parenthetical.