I would also respond with Jason's wording.
I also think some people use this as a bargaining tool. They really don't have someone lined up to make it for the cheaper price, but they're seeing if you are willing to come down at all. I had someone do that once and I politely wrote back "best of luck with your event, keep us in mind for future occassions, yadda yadda". A week later they emailed that their other baker "fell through" and could I still do it? I'm fairly certain there was no other baker and since I held firm on my price, I wound up getting it.
I don't know... maybe it's b/c this is not my main source of income, but my philosophy is that my price is set and it reflects the value of time spent away from my family. If someone doesn't want to pay it, then I'd rather have those hours free. I don't feel bad at all when someone says no because of price. If they say no because they don't like my cake or design, that's a different story.