It's not true. Even though the vast majority of a tech company's cost were engineers, they also all grew like crazy and made much more (and grew even more) than

It's not true. Even though the vast majority of a tech company's cost were engineers, they also all grew like crazy and made much more (and grew even more) than they paid in salaries. The OP is correct, if it was just about salaries. These companies would have grown far more and hired far more endlessly, but the complexity of software at that scale makes diminishing returns from hiring more.