Lower-priced cels just aren't going to generate 
the kind of profit that some sellers want any 
more, and thus you will tend to see more higher-
end (sure-seller) cels and much less of the lower-
end stuff.

Also, some sellers are protesting the new charges 
by not using YJ right now.  That resentment may 
die down in the future and you may see a gradual 
return of these people.

It's a shame for many bidders right now, because 
the competition among them must be becoming much 
fiercer right now.

The economic situation may also be tight for many 
collectors, because quite a few cels I have seen 
would be insane to let go of unless you needed 
to.  So that may also explain the presence of 
more higher end cels.