Google will reportedly pay USD $9 billion over 2018 to remain the default search engine for the Safari browser. This price may go up to as much as $12 billion next year. However, due to the growing popularity of Apple's devices, the privilege may be worth the cost to Google.
https://www.notebookcheck.net/Google-is-shelling-out-billions-to-remain-the-default-search-engine-for-Apple-s-Safari-browser.336478.0.html