There have been studies on the topic: https://www.nytimes.com/2016/04/10/education/edlife/why-upperclassmen-pay-more-they-may-get-less.html
According to this article, in dollar amounts, there is an average loss 0f $1,000 from the average institutional grant of $15,800. However, it is unclear whether this is because an average of 6% of students lose their eligibility because of low GPA, or because, on average, the amounts drops by 6% because of dropping GPAs. My guess is that the former is the most common case.
The analysis was from 2011-2012, but there is no reason to suppose that it has changed.
The data is here: https://nces.ed.gov/surveys/npsas/index.asp
However, you may have to do your own analysis.