cha-ching!, excl. — Green’s Dictionary of Slang

cha-ching! excl.

[echoic of the sound of a cash register and popularized by the film Wayne’s World (1992); it can still be used in the context of money, but refers more commonly to general pleasures, esp. a passing pretty woman]

(US teen) an excl. used to signify that something or someone has made one happy.

1997–2002		Hope College ‘Dict. of New Terms’ 🌐 cha ching int. The act of being excited when you get a lot of money, or something great happening. [...] Derived from people hearing what a cash register does when it opens.
20001		ZDNet 23 Feb. [headline] A killer camera for under $1,000? Cha-ching! The wait is over.