If you're uncomfortable or worried about insulting, say it like this "Are you negotiable on your rates at all?" or "My budget is a bit lower than that but I really love your work, is there any way we can tweak the package to make it work?"
I usually asked what their pricing was, and then when I received a quote I either said that my budget was $xxx and what could I get for that price or said that I was looking for something that would work better for my budget.
The only issue with the second thing is that sometimes they as for your budget.
I never tried negotiating, but when my lighting quote was out of budget, they lowered the cost to keep my business. Some companies will work with you, but the people who book super quick know that someone will book at their asking price so they aren't necessarily swayed to lower their prices to your budget. The wedding industry is booming and it looks like you might have time to shop around to get the best deals. Also, if you hit up bridal shows, some companies will offer discounts if you book with them then.