Revenues (official data): ~$50B/year, down from $80B/year a year ago.
Costs attributed to China are very hard to measure. A lot of the official "manufacturing cost" of the iPhone doesn't actually stay in China (as chips, screens, etc. are all manufactured outside of China, and simply assembled there: https://www.bloomberg.com/opinion/articles/2019-06-12/apple-...). According to one source (https://theconversation.com/we-estimate-china-only-makes-8-4...), about ~$8-9/phone stays in China. Also, Apple makes ~200M iPhones a year (not all of them in China, but let's ignore that).
Assuming my numbers are not too far off, Apple contributes ~200M x $10, or just ~$2B to the Chinese economy by manufacturing the iPhones there.
It seems that if China restricts (or even merely discourages) people from buying Apple products, it will hurt Apple a lot more than Apple could ever hurt China.
Of course, China cannot do anything to Apple without US retaliating. But as the trade conflict escalates, this threat loses its power as there are fewer things to retaliate with.