How is purchasing RAM identical to what Apple uses at market prices (rather than marked up by a factor of 2x to 5x) "cheating", exactly? RAM and storage prices

How is purchasing RAM identical to what Apple uses at market prices (rather than marked up by a factor of 2x to 5x) "cheating", exactly? RAM and storage prices fall drastically with time while memory and storage requirements in software increase with time. If I plan to get 3-5 years of life out of my computer isn't it only logical to add on memory and storage when I need it, not all up front?