I sometimes end up with REALLY dirty keycaps that look like they've been buried in the mud for decades. I usually use soap and denture tablets to clean them, but then I still have to through every single keycap and wipe it down which gets very monotonous, very fast. I'm hoping there is a decent ultrasonic cleaner for under $50 or so that will do at least 80-90% of the work for me, if such a device exists.