You know there's other strategies? Companies can be more clever than naively undercutting each other...

Memory in particular ... https://en.wikipedia.org/wiki/DRAM_price_fixing_scandal

The entry-cost to getting into memory is on the order of $billions and years - you can do just about anything...

Only in the most naive sense.

If it costs you $1B and five years to build out new supply and you think demand will not sustain for more than three years, it does not make sense to expand supply.

Instead you will maintain your margins currently and await demand to decrease back to your current supply.

This is pretty common and as others have pointed out is even more common in markets where competition is slow and lead times are long.

Ammunition is a great example over the last decade or so as political turnover caused relatively short lived demand spikes and manufacturers didn't expand supply because they knew once political winds shift, demand would decrease.

There's very few manufacturers, I believe 3 globally? And there's a large moat. Nobody can compete with them in the next 10 years. It's really not hard to coordinate action between 3 companies.