https://techcrunch.com/2019/04/18/amazon-music-echo-ads/

Amazon today announced the launch of a free, ad-supported music service in the U.S. that will be available to anyone who wants to play free music on their Echo speaker.

Until today, Echo owners who wanted to stream music from Amazon could either pay for an annual Prime membership for access to Prime Music, or they could pay $3.99 per month to stream from Amazon Music Unlimited (or $9.99/month to stream on non-Echo devices, as well.)