Your are conflating asset price inflation and cost inflation, they are not the same. Apple could lose $2T in market cap next week, the cost of the fab would not be discounted in the same way.
Ok, but let's say the scenario is that Apple, Google, Microsoft need to build a chip plant for 0.5nm chips. They need $1 trillion.
If each company is worth $20 trillion in 20 years, they can easily raise $1 trillion together by selling some shares or using their shares as leverage or just straight up using their cash flow. I'm simplifying things by ignoring inflation, but you get the point.
The bottom line is, if capitalism thinks a $1 trillion fab will produce more than $1 trillion in value, it will happen.
This appears to be missing the forest for the trees.
Which is to say, if Rock's law continues to hold, it doesn't matter if some global consortium can pull together $1T for a new fab; can they pull together $2T four years later? And $4T four years after that? And $8T? $16T? To say that a doubling at this rate is sustainable is to suggest that you more than double the value at each step. At some point this can clearly not be the case, unless you want to posit a world where going from one process node to the next literally doubles the entire productive output of the human race.
Absent some unforeseeable technological breakthrough, at some point it has to slow down, either slowly, or drastically, or otherwise stop altogether. And for anyone who's currently middle age or younger, it's currently projected to happen in your lifetime.
