At the Google for Games Summit, Google announced new incentives for developers who publish their games on Stadia.
70% Subscription Revenue Share

Any new game claimed (for free) with a subscription to Stadia Pro will earn a slice of revenue from Pro subscriptions, divvied up from 70% of Goggle’s earnings. The revenue share is calculated by number of days a player plays the developer’s game.
Click-to-Play Bonus

Google calls this their affiliate marketing program. As part of their advertising, developers can share a link to their game page on the Stadia store. New players who start a free trial of Stadia Pro and then go on to pay for a subscription will net the developer $10.
85/15 Revenue Split

From October 1st through 2023, all new games released will earn 85% of the game’s sales, to a maximum of $3 million. This share (though temporary and applicable to new releases only) compares to an 88/12 split for both Epic Games Store and Microsoft PC Games Store, and 70/30 for Steam, though that share improves to 25% at $10 million in sales and 20% at $50 million in sales.
Games Industry has a great interview with Google on these announcements.