The ka-ching is based on the real sound of mechanical cash registers, whose bell and drawer became a universal shorthand for a completed sale long before memes. Online, the short clip spread through soundboards and short video edits as a reaction for anything involving money. Editors keep returning to it because it needs no setup, works even on mute-adjacent cuts where the visual shows a price, and instantly changes a neutral moment into a joke about profit, spending or success.