Today Woot is offering very good used
Echo Inputs for $10, with free shipping if you have Amazon Prime. The Input is functionally an Echo Dot without a speaker. It works by connecting to a powered speaker/audio system through its 3.5mm stereo analog output or Bluetooth. I am posting here because for those who primarily listen to Amazon Music, Spotify, Apple Music, Pandora, or a few other streaming services, it provides the cheapest way I know of to stream music wirelessly without tying up your phone. Built in Mic, so full Echo Assistant/Intrusion functionality...but you can turn off the mic.
Most of the time these sell for $35, (strange as that is what Echo Dots often sell for). Currently and frequently Amazon sells them for $20 new, so this is half that.
If you have not collected old stock Chromecast Audios this is a cheap alternative that does some, but not all, of the same things. Notably you cannot stream your music files, or unsupported services like Tidal. If course, if you talk to your Chromecast Audio it does not tell your the weather or turn off the lights. This is the cheapest I have heard of a device of this type.