The ka-ching cash register sound comes from the long familiar sound language of mechanical tills and retail checkouts. It became a standard stock effect in video editing, games, and meme clips because audiences instantly connect it with money, sales, and profit. Online, it is often used the same way creators use a ding sound effect for a quick payoff cue, but with a more specific money meaning. Its staying power comes from being short, readable, and useful in everything from comedy edits to shopping and finance videos.