For every buyer, there is a seller so the amount of money involved always remains the same. Money just changes hands, regardless of what happens to the price of the stock. The money supply remains the same even with frictional costs (commissions, B/A slippage, etc.).
For example, there are 3 people (A, B, and C). Each one has $10 and A owns the stock. That’s $30 in existence. Assume no transactional costs.
B buys the stock from A for $5. Now B has the stock.
A has $15, B has $5 and the stock, and C has $10.
Now B sells the stock to C for $3
A now has $15, B has $8, and C has $7 and the stock.
Suppose the company goes bankrupt and the stock is delisted.
A still has $15, B still has $8, and C still has $7 but no stock. Again, no money vanished. $30 is still in existence.
So when share price drops significantly (the past two weeks), billions of dollars paper wealth is wiped out.