I remember when I started collecting cels 3 years ago that FY
cels were extremely expensive as the studio had not released them.
Prices started coming down when the studio released the OVA cels
and Studio Pierrot went on and released a good bit of the TV show cels
now too.  So, just a case of supply and demand.  You used to have to pay
out the nose even for a low grade cel, but now you can find some pretty 
nice cels for very affordable prices.