This is exactly why I don't post my cels for sale on this 
forum.  It's people like you who make the hobby 
unpleasant.  Many of my DBZ cels have dropped in 
value that's true, but as others have mentioned there 
will always be cels from ANY anime that are from 
memorable scenes or are from key characters that 
make the price go up.  DBZ introduced many to anime 
including myself and therefore hold a special place in 
some hearts.  

To trash an anime that someone is interested in is out 
of line.  There are probably shows you like that other 
collectors wouldn't understand the attraction to.  There 
is not one show out there anime wise that every single 
person enjoy.  There will be fans and critics too all, but 
the mature thing to do is keep your opinions to yourself 
so as not to hurt feelings of others who truly enjoy it.  
You say DBZ is liked by 14 year old kids, but in reality 
you've acted like a 10 year old with your posts.  

True DBZ cels may go down in price in five years, but 
that holds true for ANY show after it has peaked.  I've 
spent a chunk of change on Inuyasha cels and I realize 
they may not be worth as much years from now after the 
shows dies down.  That's a risk you take collecting a 
show you love.  

The fact you started a flame war over someone simply 
trying to sell is lame.  Anyone who collects from that 
series knows those two cels are from awesome scenes 
in the show and any true fan with the money would kill 
for those cels.  I know I would jump on them had I not 
purchased some Inuyasha cels recently.  

You may know the basics of how this hobby works with 
prices fluctuating, but you don't know jack about DBZ 
collecting itself or how to be considerate of others.