Wait until you have $10,000 on you, and now head to Moxxxi's bar. Go the tip jar which is right in front of her.
rapidly 10 times.
Now press the
button (don't wait for the cheev to pop)
As soon as the cheev pops, press
and choose Quit.
Now reload the game and your save and you never lost the $10,000 but you are 10GS richer :)