It’s rare for a large fraction of grant money to be siphoned to a Dean’s discretionary fund. Typically some smallish fraction (maybe 10%, often significantly less) of indirect costs (which, depending on the funder and the negotiated F&A rate may be anywhere from 0% or nearly 100% on top of the direct costs that fund the research staff and materials, etc.) goes back to the subdivision overseen by that Dean to do with as they please. Everywhere I’ve worked, that amounts to a few (low single digit) percent of total costs being used in the way you describe. And many places return none of indirects to the unit overseeing the PI and so then it’s a cool zero percent.