[resf]

If I buy a grain of sand from you for $10, have I just massively expanded the number of dollars in existence?

Market capitalisations != money.

[pharrington]

Market capitalization general corresponds with the amount of debt a company is able to take on, and the creation of debt literally is the creation of money.

[maneesh]

Yes. If you create an etf or stock index or public stock, you have massively created the number of dollars in existence.