A firm with good researchers, whose newly minted students also did good work, would soon have the suitable reputation. And those letters after your name are only as valuable as the reputation of the institution.
UC Berkeley (2016): 57%
MIT (2018): 59%
Harvard (2018): 59%
Stanford (2018): 57%
This story, from 2013, gives some of the context and history, as well as averages for universities and other research insitutions (which can have much higher overheads):
http://www.nature.com/news/indirect-costs-keeping-the-lights...
In addition, newer companies seem to just license/use the research that comes out of universities (which has the aforementioned labor model) than take on the responsibilities themselves. (at least that has been my impression, but happy to be shown the err in my beliefs)
Except perhaps in history