> during the internet bubble of 1998-2000, the p/e ratios were much higher
That is true, the current players are more profitable, but the weight in SPX percentages looks to be much higher today.
(I think a reasonable argument can be made that P/E ratios today should be higher than the historical mean, or rather that they should have trended up over time, based on fundamental changes in how companies compensate their shareholders.)
If Elon tried to sell every share of Tesla tomorrow, he would get a lot less than the face value of all his shares.
So in other words, there doesn't need to be that much currency, just that much hype.