I'm quite sure you're correct. When stacked against however much Google was going to charge (I assume more than zero), Cloudflare's incentives seem pretty clear to me.
Yeah....In the article, it says that Google wanted to charge millions of dollars and that Cloudflare did not think hCaptcha trying to pay them was sustainable, so they agreed to pay hCaptcha a large amount, but only a fraction of what Google would charge.