The capital (heh) mistake in the whole assumption that these companies are worth that much is that they'll crash the economy in their zeal to get there. And when the economy goes down the drain so do the expenditures because in the end the companies that could spend money on AI are taking that money out of the economy to put it in the pockets of a tiny fraction of society. You can only do that if you are willing to leave the rest without food on the table and that sort of move is simply not very wise.