https://9to5mac.com/2022/09/09/doj-antitrust-action/
Neither company discloses the percentage or amount, instead just hiding it in the bucket of Services revenue. However, a lawsuit revealed that it was a billion dollars way back in 2014.
Since then, the sum is believed to have increased dramatically, with informed estimates of $3B in 2017, tripling to $9B in 2018, increasing to $15B last year, and estimated to be $18-20B this year.
Taking the last four quarters as an example, Apple’s total declared Services revenue was just over $77B. If $15B of that was from Google, that’s 19%. Even by Apple standards, that’s a huge sum of money.