True, every trade needs a buyer and a seller. But value can still be lost overall when assets decline in price due to factors like bankruptcies or economic crises—meaning the “wealth” itself shrinks, not just moves between hands.
If you had purchased the shared of GoPro(GPRO) at their absolute all-time high, you'd now have lost 99% of your invested capital. Not a great ROI, I'd say. But that doesn't mean someone else has won what I lost.
Someone else has won what you lost LOL they did because they did not lose what you lost they transfer it to you! someone and their hard earned money was on the other side of that trade it was not a ghost - and he was saved from what you suffered. People that don't understand this have never owned their own business; they have always worked for someone else that has experienced this stuff first hand, I am guessing. Also just like people can't understand how you can sell something you don't own by shorting the market, the whole professional industry just loves this perpetuating ignorance.
It’s not always a simple case of one trader winning what another loses. Sometimes the whole market takes a hit, and real value just disappears. It’s easy to forget that in all the talk about winners and losers.