Comment by Tuna-Fish

> For example, I assume a fab runs for about 20-30 years.

If only.

20 years ago, fabs were being built to use 90nm class technology. Chips made on such an old node are so cheap today it can't pay even fraction of a percent of the capital costs of the plant per year. So all of it's capital has to have been depreciated a long time ago.

The oldest process node in high-volume production for memory is currently 1α, which started production in January 2021. It is no longer capable of making high-end products and is definitely legacy, and also has to have essentially depreciated all of the capital costs. The time a high-end fab stays high-end and can command premium prices, and during which it has to depreciate all the capital is ~3-5 years. After that either you push the plant to produce legacy/low price and low margin items, or you rebuild it with new tools with costs >$10B.

Also, even if fabs did last 20-30 years, the capital costs would dominate.

> And wouldn't "wildly variable borrowing costs" also affect oil and gas who need to finance the research phase and construction of the plant?

I don't understand? Nothing else costs anywhere near as much capital to produce than silicon chips. Thanks to the inexorable force of Moore's second law, fabs are machines that turn capital investment into salable product, nothing like it has ever existed before.