How does the market for numeric optimization software divided by the number of engineers required to create and maintain it compare to the market for "nearly any physical good, cloud computing, eyeballs-for-ads, watching videos, connecting with other humans, high quality computers and mobile devices, maps, email, and search" divided by the [larger] number of engineers required to create and maintain it?

Sales / potential gross profit per FAANG employee is high.

I believe the main reason is that the skillset in this domain has a small overlap with what is needed at FAANG. This is done mostly in academia and as such the salaries are in line with the salaries at universities.

I know some mathematician working for big chemical company which has a huge internal Fortran Software stack for numerical optimization.