Amazon (link for reference only) offers Prime Members: Echo Dot Gen 3 (Charcoal) for $18.99 when you order thru Voice Shopping via an Alexa-Enabled Device or the Alexa App (Android or iOS). Shipping is free.
Note, you must order through Voice Shopping via an Alexa Enabled Device or Alexa App to receive the "Alexa Exclusive Savings" price. To purchase via Voice Shopping, just say "Alexa, order an Echo Dot."
https://amazon.com