I'm not convinced that Apple's 8GB RAM costs them $50-70.
I'm just looking around the internet for LPDDR4X prices. Found this. 32GB of LPDDR4X costs only $13.40 which sounds about right. Apple probably gets it for even cheaper. There is no way in hell that I believe 8GB of LPDDR4X RAM costs Apple more than the SoC itself, even if the RAM is slightly customized and packaged with the SoC.
That’s Gb, not GB 32Gb is 4 GB.The RAM Apple uses has 4 times as many BGA pins as commonly available LPDDR4X modules. It was speculated by more knowledgeable people that the high pinout is used to operate the RAM at much lower voltages to reduce the power consumption. I have no idea how expensive such custom chip would be.