Apparently I've got a bit of an odd take on this. I've only asked for a lower price once -- it was the last day of the NARBC show at Tinley, I wanted two animals and was a little short on cash in my pocket so I offered what I had.
Generally the way I see it is the breeder prices the animals at what he/she thinks they are worth. Now if you go in offering a lower price, you're saying that those animals aren't worth what the breeder thinks. To me that just seems disrespectful.