Hang on, I have to agree here.

Offering to pay a fair price for a good cel is 
HARDLY rude!!  If it's a particularly expensive 
piece, suggesting a payment plan or delayed 
payment is a very reasonable option.  Now, that 
doesn't mean that the prospective seller has to 
ACCEPT, but it sure as heck isn't rude to ask!

Offering an unfair lowball price for a nice cel 
just because you know the seller is desperate, 
THAT'S rude.

Cancelling an order without good reason, THAT'S 
rude.

Talking with your mouth full of pickled squid 
tentacles... THAT'S rude.

Funny, mind you, but rude.