15k under budget so she goes and pays $100 too much for what should be a $30 keyboard.

Tell her it's not what you expected and not what you needed. Apologize that you wont be using it but instant that if anyone in the office needs an upgrade you are sure they will love it.

I would further, shortly, explain that building keyboards is a bit of a hobby for you and a store bought board would be like handing a TV dinner to a chief.