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