Most of the people buying an $800 MacBook Air or lower memory variant of an Apple device are not worried about RAM and don’t use it in such a way that it matters. Yes, if you’re a professional using a macOS device you can pay the $400 premium for the highest memory variant. You either have the money to pay it, or the product justifies the amount. They are charging what their customers are willing to pay, it’s also somewhat inflated because the cost of maintaining those less popular SKUs.

Last point I’ll make on this topic, you are going to see more CPUs move to have RAM on die because of the physical limitations on latency. Modern storage speeds are also making this a moot point as RAM may become just another caching layer for ultra fast solid state storage.