I've been a rabid drooling fangirl hunting 
everywhere for YnM sketches and I never saw 1 
production sketch anywhere on the net, for sale 
or not.  The only things hanging around are the 
character settei.. though even those could be 
copies-of-copies so you never really know if 
you're getting something physically from the 
studio.  I've seen the settei go for $107 (what 
i paid, i have scans in my gallery too if 
interested) to about $160.  Never saw any actual 
production material though *cries*  

I dunno how studios do these things, but perhaps 
they just were never released to the public?  Im 
hoping thats the case and that eventually they 
will be and they will start showing up... it 
will be a shame if they just never surface...

If anyone else has info, please post! ^_^