The total payment to Apple is roughly inlined with Apple's growth on total active devices using Google. i.e Devices excluding China. [0] So every two to three years you will read how Google is paying more to Apple. Except Active Devices hasn't grown much at all. Google is effectively paying 50% premium to Apple to outbid a hypothetical Microsoft bid.
CPA Cost per acquisition are already lower for Bing, and Microsoft is running with lower margin. Traffic acquisition costs for Google has been steady. And if it is a dramatic 50% increase, I am pretty sure there will be some words on it in their Quarterly Report.
In the past if this was coming from those usual suspect of Apple's PR site, you can instantly tell it is Apple's propaganda machine in the work. And this isn't the first time [1] they are doing it to put pressure on both companies either. But this time it is coming from "analyst".
To put $15B into perspective Google will be paying 10% of their annual revenue to Apple.
There is a possibility that Apple is trying to recope a potential lost of App Store revenue which is included in the same services category as the search deal.
[0] I actually believe it is closer to active user than active devices. Since a single user could have two or more Apple devices. But active devices is the only figure that Apple publish so we use that to keep things simple.