Firebase Authentication vs Google Identity Toolkit

Question

I see firebase has no server authentication API's added in the Firebase Admin but has only user management (CreateUser and UpdateUser).

Firebase only offers signin through client libraries where it depends on Google Identity Platform (https://www.googleapis.com/identitytoolkit/v3/relyingparty/verifyPassword)

After exploring further I ended up finding Firebase Auth REST API over (Implemented it too and works great) here. This API reference is great for implementing Auth through REST API and avoiding dependency on client libraries. As this helps in having complete server side authentication through cloud functions.

Coming to the pricing, Firebase mentions that Auth costs nothing where as Google Identity platforms has really high pricing.

So would like to know what Firebase team has to say on this or any one who explored this.