I agree with most people here. It depends on the quality of the animal, the haggler's offer, the listed price, people's attitudes, etc.

I did haggle with one breeder once. We came to an agreement ($530 for a $600 animal), and though the breeder seemed fine with it, I felt bad afterward--especially since it was my first morph and this particular snake got me interested in breeding. I'd like to offer some kind of repayment for his generosity, but I don't know if he'll accept it!