PG acknowledged that growth is limited by market size. Markets to support "avogadrillionaire" level wealth may not current exist.
However, there obviously exist markets to support billionaire level wealth, as evidenced by the at least 30 billionaires produced by YC, and the many others.
No, because they are ultimately constrained by outputs that can be delivered or (assuming claims on future economic output into the market) the money supply that can be assigned to the future output. Even with leverage I couldn't ask my bank to loan me 6e23 USD without a lot more stuff having to happen first.
There are markets that can grow fast of course, but once that exceeds the overall economy it can only come from forcing other markets to shrink, and that limits the growth rate to which the fast-growing market can ultimately attain.
However, there obviously exist markets to support billionaire level wealth, as evidenced by the at least 30 billionaires produced by YC, and the many others.