Cost of developing a Google Assistant App?

Question

What costs are involved with developing and/or releasing a Google Assistant App?

eg: Can you develop an app using DialogFlow and a backend (say Firebase) without having to pay while you learn?

Answer 1

First of all - you don't need to use Dialogflow or Firebase to develop your action. Both are suggested, but neither are required. You can use any NLP you want, or none at all if you use the Actions SDK (but you want an NLP). You can use any backend at all, including running it off your local machine and tunneling to it via ngrok, but you don't want to do that for production.

But, during development (and even during a light deployment before your action becomes massively popular and a stand-out hit), you have lots of solutions that will be free.

Dialogflow is free for use with the Google Assistant. Period. There is an Enterprise edition which offers additional services and support for a cost, but you won't need them. There are restrictions, but you won't bump into them until you hit 3 requests per second - which you shouldn't during development.

Firebase's free tier (the Spark Plan) is good for very simple experimentation, but once you start doing network calls to outside Google's network (if you are trying to call the network API for other services), you will be blocked. No worries! The "Blaze Plan" paid tier does require a way to bill you, but they don't start billing you until you get quite a bit of usage: 2 million function calls / month and similarly scaled usage of CPU, memory, and network. So even the "Blaze Plan" will be free during development (and for basic usage).

Updated, December 2020

Things have changed a bit since the original answer was posted, but the underlying basics remain true - there is no charge to develop for Actions on Google.

Dialogflow now has an "Essentials" edition and a more advanced "CX" edition. While you can still use both to build Actions, they're not really intended for this purpose anymore.

Instead, Google has included the Actions Builder into the Actions Console to handle the NLP work. The Actions SDK works with this, but can also just pass along all the STT information to your webhook. Both are also free to use.