While it’s a well-known fact that Google has an agreement in place with Apple to stay the default search engine in Safari on iOS, it’s never been clear exactly how much that agreement is worth. However, according to a new estimate by analyst Rod Hall, via Business Insider, Google is paying Apple around $9 billion per year to keep their agreement in place. Hall speculates that the price of the agreement could potentially rise to as much as $12 billion in 2019. He also mentions that Apple is a significant traffic driver for Google, so it may be worth it for the company to pay the considerable cost.

Apple could easily switch to another search engine if Google stopped shelling out. It already uses Bing when Siri searches the web.