I think this could be a bit of a loaded question, because maybe the lower you go or depending on what you target the implications are super big (eg IDK, fund clasp, or some alternative C compiler or OS dev work -- the idea being that given enough time and interest if money is no object then eventually they would find technical success in some respect).

but! I would probably just give a bunch of money to the qutebrowser dev, The-Compiler. Mostly I'm a fan of the verbose communication style he runs the project with -- I feel like the path from issue to current status or where to start on dev is fairly clear, even on things that are years old at this point.

Maybe the same could be said of the doom-emacs author, hlissner. I'm not a doom emacs user but the doom base seems nice and I'll snipe stuff from time to time. The few times I've reached out it's resulted in near instant changes to the doom emacs core.

Maybe some money to the wlroots devs.

Maybe FSF if I felt it would come back to emacs in some way.

hm... I guess maybe most projects I'd write a blank check to have a bus factor of ~1, and is stuff I use or have an interest in using in the future.