The cha-ching register sound dates back to mechanical cash registers from the early 1900s, whose bells rang with every sale, and the effect has been a staple of cartoons, sitcoms and game shows for decades. On modern meme soundboards it is used as a quick cash punchline, sitting alongside other classic reaction sounds like the ding. Short meme sounds like this keep it alive because the meaning is global: no words are needed to say money just happened.