Memory and Corporate Hierarchy

Why do we have the memory architectures i.e. hard disk, DRAMs, cache and other layers of memory?

The simplest and precise answer to this may be so that we can get the best available performace (cache memory) at the lowest cost per bit (HDD). Now what is the connection between memory hierarchy and corporate hierarchy??

This observation was brought about by one of the senior and intelligent guys in our company. According to him Principal engineers are the CACHE, very costly to the company but at the same time have a lot of knowledge and experience (performance). The junior engineers are the HDD, cheap and less experienced. The senior engineers and others in between acts as buffers like the DRAMs. Thus when the company looks down, it sees the best knowledge and experience at the cheapest cost!!

This is just one example, if you look carefully you may find similar analogies in your daily life to most of the engineering solutions :)