This is a big one: its a browser they don't have to pay to have google made the default search engine: https://www.cnbc.com/2017/08/14/google-paying-apple-3-billio...

It lets them use it as a jumping off point for some hardware: https://www.google.com/chromebook/find/?utm_source=en-ha-na-...

And it appears they now have an enterprise version: https://www.blog.google/topics/connected-workspaces/introduc...

I'm sure there's more, but I imagine, financially, I could have stopped after the first one.