This achievement is for earning the jackpot on the slot machine.
You first encounter the slot machines in Zone 4. After defeating 29 monsters, a door will open up with an area filled with Slot machines. You can start up one of the slot machines with the
button. The jackpot is for hitting 3 sevens. This will earn you $10,000. There is no real strategy here, as this achievement is entirely luck-based. You might unlock this achievement on your 4 try or your 400th try. Going for this achievement earlier rather than later is a better plan, as you'll have more cash to spend on weapon upgrades and miscellaneous costumes.