If the A invests $1000 in bitcoin, then the next day the price of bitcoin drops dramatically and the A loses $1000, which makes me curious, where does the $1000 A money go?
Wow!! Just wow!!!
The 1000$ have gone to the person who sold A the coins.
No matter if the price goes up or down, those 1000$ are there, in the pocket of person B.
Think of it like buying anything else a house, a car, an ice cream.
If you buy a 2$ icecream and you eat the 2$ have vaporized?
If you crash the car, if your neighborhood light up your attic, it's the same...