You seem to be confused between mesh and texture.  The hair is pretty much a solid chunk of plastic, which is then textured with color and painted streaks of hair.  The hair is then brought out by a trans map, which gives the illusion of strands of hair where they used to be streaks.

So a "touchable" series of texture maps paints smaller streaks of hair, and makes tighter transmaps, which give the illusion of denser, tinier hairs.  This is futhered along by making better highlights and other node settings to bring out realism. 

It has been a long-standing tradition in the poser community to follow the business model of releasing a hair prop or cr2 with crappy maps so that someone else can come along and sell  you another pack to make it look good.  (This is true of more than just hair.)