that was kinda rude and uncalled for.

Think what you want, but douga/genga have been 
becoming much more popular lately, due to their 
being the only things you can get from recent 
anime.  Granted, all of DBZ was done with cels, 
but that doesn't take away from the rarity of 
some sequences.  In all honesty that is probably 
one of the most saught after sequences of vegeta 
in the entire series.  Cels from it easily sell 
for several thousand dollars... so whos to say 
the sketches won't get 300 each... sure it seems 
steap... and for a single douga, not sure it 
will reach it... but for people that will never 
have a chance at owning a cel from that 
sequence, it might be as close as they can get.

I think it was a bit uncalled for, for you to 
blatantly say the seller 'IS' ripping someone 
off... because it's all in how you look at it.  
Just because you're not willing to pay $300 for 
a single sketch doesn't mean there aren't a 
bunch of others out there who are.  Many people 
these days are only collecting sketches, and in 
a lot of cases, they seem to be selling better 
than cels these days.  So who knows what'll 
happen in the end.

just my opinion, and good luck to the seller!
~yaten