RAM vs Hardisk

Sir

I do have a question?

We have a space in harddisk ,called virtual memory.  In addition to DRAM ,Operating System  uses this  virtual memory to store and run applications. Virtual memory makes up for the need of space required.

I think that the physical memory DRAM is not needed. Virtual memory inside the hard disk is  sufficient. 

By avoiding DRAM we  can save the cost of  physical DRAM. We can also save lot of time that is involved in associating the pages between DRAM and Virtual memory.

Of course , virtual memory provided by the hard disk is slow. But  in current trends we can research , to increase the speed of magnetic drums being used by the harddisk to store data. 

Thanks ,

Ramkumar.