Cover the two PhD students at the NIH payscales for PhD students on a standard training grant[1] ($43,894 not including benefits) and you've used up over a quarter of your budget on less than half the salary needs, completely ignoring any research costs that need to be covered on top of the much higher payscales of the professors. Plus a large number of PhD students in this kind of work make more than the states stipend above. Not extravagant.

https://osr.ucsf.edu/news/nih-update-ruth-l-kirschstein-nati....