https://techcrunch.com/2019/01/11/google-cans-the-chromecast-audio/

The Chromecast Audio is no more. Google has decided to stop manufacturing the audio dongle that allowed you to add any ‘dumb’ speaker to your Google Cast setup. If you still want one, you’ll have to hurry — and to entice you to buy a discontinued product, Google is now selling its remaining inventory for $15 instead of $35.

“Our product portfolio continues to evolve, and now we have a variety of products for users to enjoy audio,” Google told us  in a statement. “We have therefore stopped manufacturing our Chromecast Audio products. We will continue to offer assistance for Chromecast Audio devices, so users can continue to enjoy their music, podcasts and more.”