Wow.
I wish my team had this 'problem' Unfortunately, this year we need to raise about $2500 to cover expenses over this past season.
But I do understand the 'use it or lose it', and definitely try to maximize what you purchase, don't waste money for the sake of it. You may not think you need it now but as your team grows you may find yourself wishing you had bought a table saw or mill/lathe.
We use our table saw all the time, as Steve W said, to cut wood and lexan primarily, but with a good blade, you can rip aluminum to size. Works like a charm. Ours is a Delta saw, only a few years old, with the unifence and extender table. Something like
this
This was our team's fifth (maybe fourth?) year in FIRST, and we found ourselves using the mill/lathe more than ever. One of our seniors is very skilled on the mill and lathe from working outside of school, and he was very busy this year! We made custom gearboxes for the FP drive train, and they worked like a charm. Even simple things like drilling holes in the ends of shafts is made easier on the lathe. One like ours would fit nicely in your budget, a medium sized combination like
this
It would be a great opportunity to teach students how to use it and maybe even learn yourself! I have done a few things with it and while I'm still learning a lot, it is not complicated to use, it just takes practice and patience. Remember to budget accordingly for tooling and accessories, they cost as much as the actual machine. Somebody might jump in here with a more knowledgeable opinion.
As far as electronics go, oscilloscopes are nice to have, we have a large Textronix scope that works great for testing signals and circuits.
A battery load tester would be a great thing to have, make sure your batteries are being maintained properly. Also maybe one of those five or six battery charging stations to keep batteries fresh in competitions.
I could go on all day with this wish list, but I'll stop here, that's long enough.
-Chris