bigfatkitten parent
They apparently make enough money for TI to have continued investing, over many years, in R&D and manufacturing of those devices.
Not really?
The r&d isn't expensive because these are legacy/old type chips. There isn't much r&d happening. They're made using old processes.
Any r&d is likely using different materials. Military stuff often uses different materials for specific applications.
The profits come from raising yields, which is much easier on older nodes.