How does the MacOs High Sierra Photos Project Extensions works from the business model point of view?

In the WWDC17 session 505, Apple introduced the Photos Project Extension.

It is very interesting and the company I work for really wants to get in with it.

This session, though, did not explain what is the business model of these extensions.

How is the payment flow? How is the product ordered?

Is there any fee on for Apple?


Anybody has any info on that?


Thank you all for your time.


Alessio