Yes but why? This is what I really don't understand.

Say AGI is achieved within a reasonable timeframe. Odds are that no single company will achieve that, there will be no monopoly. If that's the case, where is the trillion dollars value for investors? From every claim we hear about it, AGI will lead to hundreds of millions of jobs disappearing (all white-collar jobs), and tens of millions of companies disappearing (all the companies that provide human-produced services). Who is going to buy your AGI-made products or services when nobody is paid anymore, when other companies, big and small, has ceased to exist? Sure, you can make extraordinary accomplishments and advance humanity far, far ahead, but who is going to pay for that? Even states won't be able to pay if their taxable population (individuals and corporations) disappear.

So where will the money come from? How does it work?