All fun and games
Until some minimum wage numpty puts the $10 note cartridge where the $1 note cartridge is supposed to be.
No, they're not keyed. They're identical, except for the bit of masking tape with "$10" and "$1" stuck on the front.
I was in a charitable mood, and I returned the $30 to the supervisor, in exchange for three ones. My compensation was seeing the employees move faster than I ever have (or ever will again), opening the machine, fixing the problem and wondering, no doubt, how many prior customers had neglected to call their attention to the matter.