For Google, it very roughly makes about $25 per year per user in 2019. But it has an estimated 4 billion users. If you can take even 1% of 1% of these users, thats still 400k users. So you're still bringing on $10m a year if you keep the same price.

Now of course Kagi is nowhere near that 400k figure, but also charges more. So you see how it can add up.