If Apple is insulated it is likely because Apple signs big contracts for large supply and manufacturers would prefer to be insulated from short-term demand shocks and have some reliability that their fabs can keep running and producing profitable chips.
As an aside, if DRAM costs stay higher we might also see renewed interest in other memory technologies (especially persistent ones) such as phase-change PRAM and magnetic MRAM that sit between DRAM and mass storage in the memory hierarchy.
And in this article you can see a photo of the memory chips attached outside of the Apple component https://www.gizmochina.com/2020/11/19/apple-mac-mini-teardow...
Big manufacturers also order their DRAM in advance with contractually negotiated pricing. They're not paying these spot market prices for every computer they ship.