For search engines, there's nothing more lucrative than being the default provider on a popular web browser. In the past, companies have paid massive amounts of money for the position; Yahoo gave Mozilla over $300 million to be the default engine for Firefox, but the company was later outbid by Google. A new report estimates that Google's place as the default iPhone search engine is costing the company $9 billion this year.

The amount of money Google is providing Apple to be the default search engine on iOS is supposed to be a tightly-guarded secret, but details leak out from time to time. As a result of Google's lawsuit with Oracle, the number from 2014 was revealed to be $1 billion. The number was based on ad revenue earned from searches on iPhones, but it's unclear if that is still the case.

New estimates from analyst firm Goldman Sachs claim Google could be paying Apple as much as $9 billion in 2018, and around $12 billion next year. "We believe this revenue is charged ratably based on the number of searches that users on Apple's platform originate from Siri or within the Safari browser," a Goldman representative said.