The kind people at Luminous Landscape have an article about a Leica factory visit in Solms, Germany (by Nick Rains).
These [Leica S2 and M9] are hand made products — quite literally. It’s why they are desirable in the first place and the process can only proceed so fast. I’m told it takes 8 hours to assemble an M9 body and having seen the care and precision with which they are assembled, I can certainly believe it.
This should explain why the quality is at the top along with the price.