https://www.ped30.com/2019/03/10/defense-apples-14-billion-r...
Edit for context: in 2018, 11.6bn or 5.1% of revenue. Compare to Amazon it's half as many dollars and 1/3 the percent.
Apple's total R&D spending is well below their contemporaries as a % of revenue.
Looking at all of the money that Google spends on research - they still make 90% of their revenue on ad sales and have had a string of failures and also rans.
No one can seriously argue that Apple’s ARM processor designs aren’t top notch, they just took over Intel’s modem division and they still depend on Intel for much of their computer hardware - except for the T2 chips that are part of their ARM designs
What else do you propose that Apple spend money on?
Horace Deidu just posted a graph on twitter showing that just their services revenue is larger than all of Apple’s revenue a decade ago.
Their spending (as percent) is approximately 1/3 of other phone makers, 1/3 of software developers, or 1/4 of other chipset manufacturers.
These numbers are all very rough of course because, as you point out, all of these companies work in multiple sectors and R&D spending is not disclosed in that much detail.