An imitation of the sound that an antique cash register would make, often used when discussing financial matters or transactions, especially some form of profit. "Ching ching" and "ka-ching" are also commonly used. We've posted some excellent sales numbers this holiday season—ching!
See also: che
exclam. the sound of a cash register, said to indicate money or imply a financial motive or success. Just got another big order. Ka-ching! Tell, me what’s important, dude. Ching! Right?